You can find A# on your 140
receipt at item Beneficiary. I found that number on my 140 receipt, it's the same number as appeared on my 485 receipt and my H1B and my J1 waiver approval notice. I don't know why, but I double checked it, it's true. However, my wife's A# on her 485 receipt is a different number with her J2 EAD A#. So strange.