No, you can't
The official ruling1 from Sage Advice Compendium
Are extradimensional spaces, such as a demiplane or the space created by rope trick, considered to be on a different plane of existence?
An extradimensional space (aka an extraplanar space) is outside other planes. Therefore, if you’re on the Material Plane and your foe is in an extradimensional space, the two of you aren’t on the same plane of existence.
The unofficial tweet from the rules designer Jeremy Crawford
If two people are on different planes of existence, they are infinitely far away from each other. For example, if I'm on the Material Plane and you're on the Ethereal Plane, we're not within 30 feet of each other.
Because you are in an extradimensional space, you and your familiar is not on the same plane of existence. Therefore, you are infinitely far away from each other. The find familiar spell says that
While your familiar is within 100 feet of you, you can communicate with it telepathically. Additionally, as an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn, gaining the benefits of any special senses that the familiar has. During this time, you are deaf and blind with regard to your own senses.
Because you're not 'within 100 feet' - you're infinitely far away by being in different plane - you cannot communicate with it telepathically and see through your familiar's eyes and hear what it hears2.
you can argue that as long as the bag is opened, you are within 100 feet by direct line from within the bag to your familiar, therefore you can use the ability. I tend to interpret it strictly that the opening does not circumvent the 100 feet requirement, though.
1 It is an official ruling how to interpret the rules as they were designed to be. However, it is only a ruling. The DM has the final say and can choose whether to use the official ruling or not.
2 'Additionally' can mean that the ability to use your familiar senses is a separate ability from the ability to communicate with your familiar, which is restricted to 100 ft. However, both abilities are within one paragraph, so 'additionally' must mean that the first ability restriction applies to the second.