移民局要求上繳I-94,是好事
1. the immigration officer should take your I-94 at the end of the interview.
2. your case go foward one more step to GC or GC stamp. hope next mail you get from BCIS is 485 approve letter.
3. after file I-485, your status change to AOS and you don't need I-94 to stay inside USA. if travel outside USA you need AP.