Trade in

We are all other users here and have no involvement with that program. You will need to deal with Apple; not sure about the way it is paid as Apple uses third party partner companies for this in most areas. And, they will not give you a definitive amount until after they have examined the device. However, from what I've heard, if the screen is cracked, you may not get anything and you do need to reveal that.

You may be better off trying to sell it yourself.

https://www.apple.com/shop/trade-in

With a dent and a crack Apple will recycle it for you but they will not give you an Apple Gift Card (which is what they do for a standalone trade in). As babowa sagely suggested, sell it as a parts phone yourself.