Bonjour Kimberley,
'sable' is not really countable in French. See examples below:
J'achète du sable = I buy sand
Il y a trois sacs de sable = there are three bags of sand
Voici trois grains de sable = here are three grains of sand
J'aime marcher dans le sable chaud = I like to walk on warm sand
J'ai traversé les sables brûlants du désert = I crossed the burning sands of the desert
I hope this is helpful.
Bonne journée !