Answer:
To find the volume of a rectangular prism, you have to first find the L (Length) H (Height) and W (Width). Then you must multiply L x H x W. The order of the L, H, and W does not matter as long as you multiply.
Example
A rectangular prism is 5 in height, 2 in length, and 8 in width. Find the volume.
H x L x W = 5 x 2 x 8
5 x 2 = 10
10 x 8 = 80
80 is the volume.
L x W x H = 2 x 8 x 5
2 x 8 = 16
16 x 5 = 80
80 is the volume.
W x H x L = 8 x 5 x 2
8 x 5 = 40
40 x 2 = 80
80 is the volume.
Hope this answers your question. (Also you can use my example as a template format in the future if you'd like.)