do we use the same box that came the new computer to send back

You should be receiving a "trade-in kit" according to How to prepare your Mac for Apple Trade In - Apple Support.

If you did not, be sure to use the "Contact Apple Support" link at the bottom of that Support Article.

cary122 wrote:

I have not received the box yet?

Use the "Get Started" link on that Support Article to find out why you have not yet received it:

"Contact Apple Support

Need more help? Save time by starting your support request online and we'll connect you to an expert."