Footage shot at 4096 x 3024 How should I interpret Bringing into Ae

99% chance this is square pixels. If there is no included audio track and metadata info you'll have to guess at the frame rate. AE's default is 30 fps. You can pick any frame rate you want if you don't have to sync audio. If you do have to sync audio I hope there is a slate somewhere.

Another important question; what is the shot going to be used for? If it is going in another film you need to know frame size and frame rate. The frame size you stated is very close to Film 4K so that might be what you are looking at. 

If this image sequence came from a camera there is a slight chance that the footage may be shot with an anamorphic lens. If that is the case you can try the 2:1 Anamorphic setting and see if things that should be round, look round. If they don't then your footage is square pixels. 

You never look like an amateur if you ask questions about the footage.