Hey, after digging out the ATPL notes this one is bugging me because I remember being able to do these and cant now!
The formula I had for doing them was:
Pallet size(metres squared) = Load(kg)/Floor Loading(kg per metre squared)
You have to convert the pallet sizes from cm to m for a start anyways.
Hope this might be some small help ill stay trying to unfreeze my brain here!