I can't remember the password in the notes app

Apple can not help you to gain access to your lost notes if you have forgotten the passcode.

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

You cannot. There is no way to reset a locked notes password. You will have to remember it if you ever wish to open those locked notes.

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

“If you forgot your notes password

To unlock a note, you need to enter the password that it's locked with. If you forgot the 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. A new password will let you password protect any notes that you create going forward with the new password.”