Volume of a prism = (area of base)(height)
Consider each prism's volume in terms of multiple layers that are each one unit high and stacked depending on the height.
Solve for the volume of each prism if it had only a 1-unit-high layer and then for the actual respective number of layers based on the height.
Volume (1 unit layer): (50m · 10m)(1m) (500m)(1m) = 500m3
Volume (Regular): (50m · 10m)(10m) (500m)(10m) = 5000m3