trading in an iMac

If you are doing an on-line order with Apple, you will be asked if you have a computer to trade in. If so, they will provide an estimate of your trade in value (subject to confirmation later). After you receive your new computer, you will be shipped a return container for the old Mac with instructions. You must return the power cord (to Apple), but not the mouse or the keyboard. Your new computer will have both - wireless units. The instructions you receive will explain in detail everything you need to know, including how to transfer your data and then how to properly clean and erase your old computer's hard drive. Enjoy your new Mac.

It depends on who you are doing the trade in with

and what they require.