The cake is not decorated, just bc covered in fondant and frozen. I wrapped in plastic wrap and foil. Should I thaw it unwrapped or leave the cake wrapped? They are not in boxes.

Ideally, they should be boxed so that during thawing no marks are left on the fondant.

I suggest removing the wrappings, place FROZEN cake in a box--quickly-- wrap box in at least 2 layers of Saran, and place in fridge for 24hrs. to defrost. Take out of fridge, still boxed and wrapped, and allow to come to room temp (at least 2-4 hrs.). Remove from box and you should be good to go.

HTH
Rae