how do I unlock a NOTES password?

You can unlock a note only when you enter the password that it's locked with. If you forgot your password, Apple can't help you regain access to your locked notes.

Source and more info at Lock notes on your iPhone, iPad, iPod touch, and Mac - Apple Support

If you have imported some notes from Old iPhone to new one then it will have to attach the password to the new Touch ID / Face ID on your new iPhone. At some given time you must have created a password and enabled touch Id / Face ID to the password. Any Notes created there after will only use your Touch ID / Face ID. Because of this it ir very likely that you may not recall the password now.

Face ID / Touch IDs are not transferable from one device to another.

Watch the 2 GIFs below about locked Notes.