How to unlock notes on my iPhone XR?

Hello ~ Do you mean you need to unlock your notes perhaps? More information needed to assist. If your notes are locked and your forgot the password you do indeed have a problem. Resetting your note password will not give you access to your old notes. You will have to remember the old password…no way around it. Take a look here:

How to lock or unlock notes on your iPhone, iPad, and iPod touch - Apple Support*

*Don't forget your Notes password. Apple doesn't have access to locked notes and can’t help you access them if you forget your password. If you forget your Notes password, resetting the password doesn’t give you access to previously locked notes. Resetting then creating a new Notes password only allows you to lock other notes.

~Katana-San~