Replacing back cover : how to transfer parts ?

Hello all, i love my pixel 4a and want to use as long as possible.
The battery is bulging a lot, so i ordered a new genuine one from Ifixit with the tool kit.
But the plastic back cover of my phone is all cracked and in a very bad shape.
I ordered a nice new one from aliexpress but some things are missing like fingerprint scanner or a metal part on the top.

How to transfer those to the new back cover ? And what do i need to transfer, is there a list ?

A detailed tutorial would be very cool, because the back cover changing tutorial on ifixit doesnt show the parts transfer from the old cover to the new.

Thanks !