How do I restore Notes only from my iCloud backup?

Notes aren't stored in iCloud backups.

What does iCloud back up? - Apple Support

If the notes were recently deleted, they should be in your Recently Deleted folder in Notes:

If you're missing notes on your iPhone, iPad, or iPod touch - Apple Support

See also here:

Delete and recover notes on iCloud.com - Apple Support

You cannot selectively restore data. You would need a complete restore.