restriction passcode
How to reset restriction passcode iPad mini 3 without a computer
A: You can't reset the restriction passcode (it wouldn't be secure if you could, would it?)
B. You need a computer to erase your iPad and you can't restore from backup
If you don't have a computer, use a friends computer or schedule an appointment at your Apple Store Genius Bar.
This link explains how --> If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support
Remember, you CANNOT restore the iPad from backup. You will have to set it up as new. If you had photos, messages, etc., turned on in iCloud, you can turn them back on and they will redownload to your iPad. You can put your apps back too.