i need to reset my iphone

Settings>General>Reset>Erase All Content & Settings.

Cheers,

GB

Connect to iTunes and then back up data and then select "restore iPhone". It will walk you thru steps after that.

See here: https://support.apple.com/en-us/HT204306

What kind of passcode? Lock screen passcode? If so, then follow the instructions in this support article that best fit your circumstances:

iOS: Device Disabled

It's always easier if you provide all of the information up front.

Cheers,

GB