iPhone battery health changing

i have a iPhone 7 Plus. The battery health is at 75% so I was wondering knowing some stuff before changing it. So here’s my question, if I change it would it erase everything from my phone? Especially my pictures? Cause I have like 52K+ pictures! Plus I can’t back up these all cause my iCloud storage is full and I don’t have the money to buy more storage. So I hope y’all can help me before I change it..