If you have forgotten your password for Locked Notes, and you do not remember the Hint answer, then there is nothing that can be done.
Set up your notes password
Before you can lock your notes, create a password that you can easily remember. And make sure that you give yourself a password hint. If you forget your password, Apple can't help you reset it.
If you access your iCloud notes on more than one Apple device, you'll use the same notes password to lock and unlock all of them.
If you forgot your 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.
You can create a new password, but this won’t give you access to your old notes. But it will let you password protect any notes that you create going forward with the new password. This could lead to you having multiple notes with different passwords.
If you have multiple passwords, you can't tell which password you should use when you look at your notes in the Notes list. When you open a note locked by your old password but enter your current password, you'll see an alert that you entered the wrong password with a hint for your old one. If you then enter the correct old password, you get the option to update that note's password to your current one.
Lock notes on your iPhone, iPad, iPod touch, and Mac - Apple Support
https://support.apple.com/en-hk/HT205794