There are two easy ways:
For a cube solid- length x width x height
For rough shaped solids- using a graduated cylinder (note starting level of water), you can place an object into the water, and note the difference in the water level (this is the ending level). So take the starting volume in the cylinder, and subtract it from the ending volume, and you have the actual volume. Because it is a solid object that you are finding the volume of, the units are cm3 or cc
For a cube solid- length x width x height
For rough shaped solids- using a graduated cylinder (note starting level of water), you can place an object into the water, and note the difference in the water level (this is the ending level). So take the starting volume in the cylinder, and subtract it from the ending volume, and you have the actual volume. Because it is a solid object that you are finding the volume of, the units are cm3 or cc