I forgot my icloud backup password. How do I reset it? (NOT my Apple ID, but the password for my backup)

There is no password for an iCloud backup. There is possibly one for an iTunes backup.

All of your iCloud content, including backups, are protected by your Apple ID and password.

For your iCloud backup password help here > About encrypted backups in iTunes - Apple Support

Don't be confused by the title of the link and article.