You can find the link to your PUK-code here.
The standard PIN code of your SIM card is displayed in your account: https://mobilevikings.be/en/my-viking/settings/sims/
If you have entered the PIN code incorrectly three times, your device will require your PUK code. You can now use the puk1 code. After entering this PUK code you choose a new PIN code.