How to find my pin

PIN to what?

An iPhone or iPad uses a Passcode. (and it’s created by you)

New devices or web-access to iCloud might require a Verification Code.

A SIM might need a PIN … for that you’ll need to contact your carrier.

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

I’m not aware of anything else being termed a PIN within Apple’s Ecosystem.

If your Mac laptop was previously marked as Lost or Stolen using FindMy, it might have a special, owner-assigned Passcode; which needs to be re-entered before the laptop can be used.

See this article for more info; particularly the final section:

If your Mac is lost or stolen - Apple Support