Where can I find pages not listed?

The author/admin one can be removed by renaming your admin user to something else. There are security plugins that help you do this. But it will simply be another page for whatever you rename it to.

The category/uncategorized one is similar. You can rename the default category, but then you would have a page for whatever you rename it to. You can’t delete the default category, but you can use it (especially if it’s named something else).

I don’t know what that third one is. It looks like a Page name you made.