Cannot locate my Notes anywhere.

Set up notes with iCloud Use Notes on your iPhone, iPad and iPod touch - Apple Support 

You can use iCloud to update your notes across all of your devices. To set up Notes with iCloud, go to Settings > [your name] > iCloud, then turn on Notes. You’ll see your notes on all of the Apple devices that you’re signed in to with the same Apple ID.

And then follow the steps in the article to view notes at iCloud.com Show the folder or notes list in Notes on iCloud.com - Apple Support

make are that yo have notes selected to save in your iCloud account, so click on your name in system preferences>you>iCloud> make sure notes is selected/on.