i want to restore my backup but i forgot my password

If you're talking about the password to encrypt an iTunes backup, you can't do it, sorry.

See this support article:--> About encrypted backups on your iPhone, iPad, or iPod touch - Apple Support

There are some 3rd parties apps (ie iPhonebackupextractor) that might help you, but I never tried those apps, so I can't give you any specific suggestion.

Regards

Giulio