What can I get for my A2764 on trade in? It's only a few months old.

We are other users, not Apple. You can find out for yourself:

Apple Trade In - Apple

Please note: current models are sometimes excluded, but you can easily sell it yourself.

If you purchased this iPad from an Apple Store or Authorized Apple Retailer in the last fourteen days and it’s in like-new condition, you should be able to exchange it.