It is usually on your I-485 receipt and on the FP appointment letter too..(on the top right just above your name)
If you still cant find it, ask your attorney..
Another question about the A#:
Does assignment of a A# mean assignment of a visa number (for 485)
---------------------NO
and that I wont have to worry about the visa numbers becoming unavailable in the future? Or is the A# something different?
(As u might have guessed, I am from a retrogressed country)
Alien Number has nothing to do with Visa number A# is given by USCIS and Visa number is under DOS