MacBook Pro trade in and erase

You need to do this:

What to do before you sell, give away, or trade in your Mac - Apple Support

After you have erased your Mac, you will need to request a trade in. You can do this by going to Apple Trade In - Apple, and selecting Mac. You will need to enter your serial number and a couple of other things about your Mac, then you will need to type in your address so they can send you a box where you will send back to them with your Macbook. Hope this helps!