DON'T try and guess it !
If you do try to guess it and get it wrong a certain amount of time you will need to buy a new SIM card because you will "fry" the memory.
You need to either take it to the shop you bought it from or go onto the shops website , click help and support, type in "PUK Code" and then it should come up showing you what to do.
Sometimes you can just enter your mobile number into the website and it give you your personal code or if you can't find it you need to take it to the shop. The code isn't in any booklets it can only be given to you by your service provider.