The volume of a right rectangular prism is expressed in cubic units. To calculate the volume, you multiply the length, width, and height together.
In this case, the volume can be calculated as:
\[ \text{Volume} = \text{length} \times \text{width} \times \text{height} = 8 , \text{meters} \times 10 , \text{meters} \times 5 , \text{meters} = 400 , \text{cubic meters} \]
Therefore, the unit that would express the volume of the prism is:
cubic meters.