My Photo Stream is shutting down on July 26, 2023. Learn more about this transition and how to keep your photos up to date across all your devices and safely stored in iCloud by reading this support article --> Information about the My Photo Stream shutdown - Apple Support
"My Photo Stream" is an old precursor to iCloud Photos dating from 2011. Many people have never used it or have since transitioned to iCloud. If you don't see a My Photo Stream folder/album in iCloud Photos you don't use it and don't have to do anything.
1) Go to: Settings
2) Choose Your Name / AppleID
3) Go to iCloud
4) Go to Photos
5) See if you have My Photo Stream. If you do, read the suport article about what to do.