I forget my passcode and my phone is locked

connect it by cable to a computer and read

If you forgot your iPhone passcode or your iPhone is disabled - Apple Support

if you

don't have a computer then you will need to use a computer from a

relative/friend/public library or computer store

Hopefully you have been backing up your phone and/or synchronizing data to iCloud. Any data that exists only on the phone is as good as gone … you will need to do a restore after the reset, if you can.