Unlock computer saying needs pin

• Your Mac might ask for a PIN code when it has been remotely locked using Find My because the owner thinks the Mac is lost or stolen. Enter the four-digit or six-digit passcode to continue.

If your Mac doesn't start up all the way - Apple Support

nikia196 Said:

"Unlock computer saying needs pin: My computer is locked and saying needs a pin"

-------

Being Sold a Locked Device:

Is this a used device that was sold to you? If so, I'd say you've been scammed(though a full-assumption on my part), and should return this to the seller ASAP.