It seems to me, my good fellow, that you're planning a heist. The loot in this case consists of a caravan, but the way you'll go about pulling it off will still follow some general rules. You'll need to do the following:
1. Gather a Crew
Before you can pull off a heist, you'll need a crew to do the job. Who you have available goes a long way toward determining what plan you'll develop. You've already specified that the primary force in your crew is going to be a devilish entity, somewhere between CR 9 and 11- for no particular reason, I'm going to treat your boss man as a CR 11 Horned Devil (MM p. 74).
He won't be able to steal a small traveling caravan on his own, however- he'll need help, and you're already thinking in terms of magic (there are ways to do it without magic, but we'll focus on your stated goal of "teleporting" your loot/caravan out), so this Horned Devil needs some spellcasting minions.
Given that you're looking for a "few" minions, let's arbitrarily restrict ourselves to 3-4 crew members. The Horned Devil, in addition to running the heist, can also serve as muscle, so your other crew members need to be able to pull off the rest of the heist themselves. Given that we want to get a bunch of people teleported, get rid of their things, and don't want to worry about resistance, I suggest a Conjurer (Volo's, p. 212), Evoker (Volo's, p 214), and an Enchanter (Volo's, p. 213), with either an Illusionist (Volo's, same page as the Evoker) to cover up what you're doing or a couple prepared spells set aside for one of the other minions to pull double duty. A Bard (Volo's p. 211) would be handy for their ability to cast silence, but isn't strictly necessary if things go well.
While you can have more minions for your devil, I'd leave them back at the lair. When pulling off a heist, smaller, leaner groups are better. After all, time is of the essence. Speaking of...
2. Research, Restrictions and Advantages
If you're the DM, you can treat a bunch of this step as already taken care of. Presumably, however, your crew has "cased" their target, figured out the caravan's typical routes, and what constraints they have to work around. You've already listed a couple- the heist must be discreet and relatively difficult to spot happening from a distance. The heist must happen in the night, during the hours when people would normally be sleeping. All the creatures in the caravan have to be teleported, and the equipment must either be teleported or, in some other way, be made to disappear. And whatever is done must either leave no trace or leave traces that can be cleaned up before the crew departs the scene.
Your crew also has several advantages. Some of these are universal- Resources are plentiful, as is preparation time. Most will be specific to your crew- the crew we're using as an example has for advantages a large number and variety of spells at their disposal, and the devil itself is more than strong enough to overcome any creature in the caravan who isn't a PC.
By this point a plan should be coming together, based on what your crew needs to do and the methods they have available to do it. Our crew has four primary goals- Get into the camp, grab the creatures, get rid of the equipment, and escape without notice. They have a matter of hours to do all of this, and they need to leave behind little in the way of clues...
3. The Plan
Your plan will be specific to your crew, but ours is going to rely heavily on a combination of brute force and misdirection. The horned devil, having plenty of time, either has the conjurer make him a permanent teleportation circle or can be assumed to already have one in his earthly lair. If everyone prepares invisibility and nondetection (or uses magic items that give the equivalent, such as dust of disappearance), they can make their way safely to the camp without being spotted. From there, depending on how large the camp is, a couple of spells are in order- fog cloud, cast at a high enough level, can completely obscure the camp, and if necessary, hallucinatory terrain can create a line of illusory trees that serve as a visual barrier. These should be sufficient to keep outsiders from seeing what is going on- the action will be taking place far enough from possible observers that the night will do the rest for you.
Once the camp is prepped, the next stage is the Assault. Your crew's goal is to subdue every creature in the camp, which can be done any number of ways- a few ideas that immediately swing to mind are castings of sleep to make sure that nonelves don't wake up as they're moved, or carefully waking up single creatures and using suggestion to convince them to come with peacefully- and there's always the option of the devil simply picking up a sleeping creature and clamping a hand over their mouth. Either way, the subdued creature is taken out of the camp entirely, because the best way to ensure that no trace is left at the camp is not to do anything overt at the camp. Instead, a prepared area nearby serves as your staging zone for the next step. For the sake of clever example, we'll say that the horned devil has planned this long enough to have a quiet cabin minutes away, with a specially prepped basement consisting of an adequately-sized cell, a wooden ramp, and a 10-foot square section of floor.
By now, the role of the crew members is becoming clear- the conjurer obscures the area, the enchanter quietly preps and removes creatures to the cabin's basement, the devil bodily takes those who won't come quietly. What of the evoker? He and the devil are responsible for destroying the evidence. Fireball at the campsite isn't an option, but a large fire in a freshly excavated hole by the cabin, its smoke dispersed by gust of wind or the like, is. If this is a caravan, it is designed to move, and the devil is more than strong enough to move everything himself, even if in parts, and it should be possible to get the entire camp moved within a couple of hours (probably much less). Once everything has been burned to the point that the remains can be covered, shovels or spells can do the rest. Castings of prestidigitation can clean up small but easily noticeable evidence. Once they've finished, it will be hard to tell that anything happened at the campsite, beyond a possible missed footprint or two.
The last step, though the primary goal, is the teleportation of the creatures. Once in their prepped cage, you don't need to worry about willingness or saves. The conjurer casts teleportation circle on the empty 10-foot square, keyed to the devil's lair. A lever is pulled, the cage tilts and opens, and all the creatures, willingly or not, slide down the ramp. From the spell's description:
Any creature that enters the portal instantly appears within 5 feet of the destination circle or in the nearest unoccupied space if that space is occupied.
There is no saving throw or willingness necessary. Creatures forced into the portal instantly go through, even if there isn't room immediately on the other side.
Any good heist has some complication to it, and even if you're trying to figure out, as a DM, how your NPC villains could pull off such a heist, it's a good idea to include a complication. There is little honor among thieves, after all, and for the purposes of this scenario your devil and his minions are indeed thieves. Possibilities include the minions being forced to help the devil take these souls in exchange for keeping their own, making them almost as unwilling as the victims, or the wizards planning to double-cross the horned devil- and the devil, well-used to duplicity, planning a double-cross of their own.
While the main steps will be pretty standard, how the plan itself looks is open to a great deal of interpretation. For example, instead of an evoker cleaning up the crime scene and the camp, a couple of magic items can be used- a sphere of annihilation will do the trick neatly, or the evoker can be mimicked with a bead from a necklace of fireballs tossed into a portable hole filled with evidence. A cubic gate could be used instead of a teleportation circle, and one of the other sides of the gate could be the final destination of the equipment. You could cast major image to make the cubic gate look like a tunnel opening. If you have time to physically destroy the items, they could be fed to a bag of devouring. Sufficient castings of darkness or the like could be used to hide what is happening. Your devil may do some of the casting themselves, depending on which one you pick, or employ a small legion of lesser devils to bodily pick up the entire camp under cover of darkness. While not quite endless, the possibilities are indeed many and varied.