Photos from a certain period of time did not transfer from old iPhone to new iPhone

I ran out of storage in my old iPhone and ended up getting a new phone 12. In the process of transferring, there is about a year and a half’s worth of photos, and a really important time ( I got married, and had a baby) all have gone missing. I have tried to figure out what went wrong but am not sure since my phone was definitely backed up on the cloud when the transfer was taking place, but you can see that albums that were made are now empty, and in my photo reel, there’s a whole 18 or more months that have just be wiped out.

I am really devastated since they aren’t showing up in my iCloud either, and I’m unclear about how to get these back. They have to be retrievable by Apple, some how. Can anyone help or point me in the direction of any really reliable services/software that might be able to to help?

[Re-Titled by Moderator]