iPhone Transfer Missing Photos

Hello! I recently got an IPhone 13 in which the cell phone carrier did the backup and transfer to my iPhone. They put my pictures onto iCloud (which I have access to) and then transferred them over to my phone. Unfortunately, a few thousand pictures are randomly not on the iCloud nor on my phone. The missing ones are pretty sporadic. For example, I have a few pictures from July 4th and a bunch of missing ones. Are they gone for good since they aren’t on my iCloud either? Help me out!! Too many missing baby pictures!!!