Unopened products that I have

Apple's return policy is generally 14 days. If outside that limit,

try the trade-in program.

This is the link for US:

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

If not in US, check Apple for your location to see if available.

As Incarnate_Blade correctly stated, because they are current generation products, they cannot be traded. So the choices are to wait for a later generation product to be released by Apple and then trade them, or sell them elsewhere.