I received my trade in box but it doesn’t contain a return shipping label

Hello lassiter91, I would get in touch with Apple Support and ask them about the Shipping Return Label.

Contact - Official Apple Support

When I received my trade-in kit, there was a shipping label on the outside of the box (for the shipment of the kit to my address). On the upper right-hand corner of this label there was some small "peel me" text. Turned out I was able to peel off the label and underneath was the return label, already attached to the box.

I had the same problem. No return label under the UPS delivery label. Even took the box to UPS store and they had no idea about Apple trade-ins. Called the 1-800 Apple Support number, told the AI chat the problem, it verified my iMac type, asked the trade-in order number, and forwarded me to a human representative. She then checked the trade-in order number and I was issued a label (this time FedEx) via email within one hour. Apple should be aware these 3rd party vendors are not supplying needed labels!