Dell sends these through a contractor. You'd have to contact them directly. There is information here: Dell Trade-In Frequently Asked Questions (US Only)  
What does it take to resolve things with Dell when they mess up? I sent them an Inspiron 3668 to their trade-in program as I was looking to upgrade my PCs. They acknowledge receiving the unit on 12/21/22 but I started asking for updates all I got was it is being escalated and someone will contact me the next day.  Yesterday I was informed that Dell's trade-in unit couldn't find said desktop as they were searching for it. At what point will someone contact me and resolve this mess? Dell is one of the worst companies to deal with unless you are looking to purchase a PC. They have lost my old desktop and are doing nothing to compensate me for my lost desktop and it's trade-in value which is hampering my ability to purchase a new PC. Talk to me Dell please I deserve some sort of resolution here for your mistake.
Dell lost my trade-in