where is the PIN in my sim card

If you enabled the SIM PIN you had to write down or remember the PIN. Without it you cannot use your phone on the cellular network. And if you enter the wrong SIM PIN 3 times the SIM will be permanently disabled and you will have to get a new SIM from your carrier.

You may be able to bypass the PIN by getting your account’s Personal Unlock Key (PUK) from your carrier, either by calling them or by visiting the user account login on their website.

That is your PUK code, see this Apple article: Use a SIM PIN for your iPhone or iPad

Use a SIM PIN for your iPhone or iPad - Apple Support

Ask your carrier for help with their SIM