I forgot my passcode on my Iphone 6s ,and now how can i do .

If your device has iOS 15.2 or later installed, check out this link→How to reset your iPhone, iPad, or iPod touch when you forgot your passcode - Apple Support. Otherwise:

See this Apple support link→If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

Or watch this companion video ⬇️

After restoring the phone using one of the methods above you can restore your most recent backup.