forgot restrictions passcode

Restore to a backup (if it was taken when the code wasn't on the device), or reset the device back to factory defaults (for both, first copy off anything that you want to keep) - to reset it back to factory defaults you may need to use recovery mode, there are instructions for doing that half-way down this page : If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - Apple Support

What is my passcode for my iPhone 6s?

Only you will know. If you can't remember follow the instructions in the link in my previous reply