You're probably going to have to recover photos from some place other than the phone, if you can recover them at all.
I could be mistaken, but I believe that we are talking about an iPhone that it is so old that it would never have been able to use iCloud Photos. Wikipedia says that iCloud Photos originally required iOS 8.1 or later – and your iPhone can't run any version of iOS that high.
iCloud backups were apparently possible with iOS 5 and later, although the only way to see what was in one would be to restore it to a phone, wiping that phone's current contents in the process. Likewise if you had backups on a Mac made with the help of iTunes.
Did you ever import photos from that phone to a computer in another way, one that might let you recover copies of photos from that computer's backups?