Baby clothes 💙

Hi ladies!! I had a doctors apppintment this morning and doc said our baby is 6 pounds 2 oz at 36 weeks and 3 days. She said not to buy "to many new born clothes." Great- that's all I got at my shower. My question is, how do I know where all of the clothes came from so I can return them for larger sizes?! I didn't get any gift receipts so the possibilities are endless. Any ideas?! Help! Haha thanks! 💙💙💙