Ok so find the volume of 1 gold bar and then see how many volumes of 1 gold bar fit into a vault of a volume of 500 cm3.
Volume of a rectangle ( 1 gold bar ) is l w h ( length width height )
632 = 36 cm3 -volume of 1 gold bar
500 / 36 = approx. 13 full gold bars will fit into the vault.
Hope this helps :D.