Q: How can you find  your restriction password if you don't remembe?

Read How to reset forgotten Restrictions password with iPhone restore?

The basis of that support document is to tell you that you cannot recover or find the restrictions passcode. You will have to restore the device to factory and you cannot use your backup since the restrictions passcode resides in the backup. You will have to start your device back as new and put individual content on it via the sync process, not using your backup.

With the link that Allan provided, or you can look at this one too. Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings - Apple Support

This also explains encrypted backups. About encrypted backups in iTunes - Apple Support

Wrong subject area.