A puk code is a security lock on the phone when you've attempted to access it (failed) to many times.
That code can only be provided by the manufacturer and is unique to each individual serial number. Call your phone provider and they will have records of your PUK code. You will have to provide proof of ownership for the phone.
*warning* PUK codes will give you an EXACT # of attempts u can try. After those attempts it destroys your sim and is not unlock-able.