Orb of Dragon’s Breath is an action, not an item.
Orb suggests a shape like a ball or a sphere; see also the spell chromatic orb. (Thank you @Carcer). While D&D Beyond lists an item called Orb of Dragonkind, no similar entry is found for an Orb of Dragon’s Breath.
The action is specifically a ranged spell attack. It is the same, be it used by a Dragonsoul or a Dragonfang. Here are the actions for a Dragonfang.
Multiattack. The dragonfang attacks twice with its shortsword.
Orb of Dragon’s Breath (2/Day). Ranged Spell Attack: +5 to hit, range 90 ft., one target. Hit: 22 (5d8) damage of the type to which the dragonfang has damage resistance.
Compare this to Hurl Flame, from the Horned Devil.
Hurl Flame. Ranged Spell Attack: +7 to hit, range 150 ft., one target. Hit: 14 (4d6) fire damage. If the target is a flammable object that isn't being worn or carried, it also catches fire.
A significant difference is that Hurl Flame is at will, while Orb of Dragon’s Breath is 2 per day (3 per day for Dragonsoul); another difference is that the orb's damage type is based on the kind of resistance to a damage type that the attacker has.
Otherwise, they are a ranged spell attack unique to that NPC / Monster.
Can it be an item?
Sure, if you want it to be. (As you noted in a comment, you are the DM). While I'd recommend against making it an item (for the sake of simplicity) if you think it would be cool for your players to recover these and use them then make it so.
At that point, as DM, consider what rarity of magic item they are (I'll guess uncommon) and whether they do or do not require attunement. (I'd suggest yes).
Most magic items that allow a user to cast spells will specify whether they do (e.g. Wand of Web) or do not (e.g. Wand of Magic Missiles) require attunement.