The standard PIN code of your SIM card is displayed in your account in the section 'Settings' > 'SIM settings'.
If you have entered the PIN code incorrectly three times, your device will require your PUK code. This code is also displayed under 'Settings' > 'SIM settings'. You can now use the puk1 code. After entering this PUK code you choose a new PIN code.
You can find the link to the PUK-code here.