My notes disappeared on my iPhone 13 Pro Max

Did you make sure you're not in the wrong folder?

i.e., hit the back-arrow in top left corner (might say 'All iCloud' or 'Folders' with a '<' symbol

Also, have you tried other devices to see if they're viewable there?

aletha132 wrote:

Notes is turned on and I have made sure icloud is turned on

Delete and recover notes on iCloud.com - Apple Support