Depends on what kind of solid it is. -_-
For cube = l³ where l = length
For cuboid = length × breadth × height
For Cylinder = πr²h where r = radius, h = height
For sphere = 4/3πr³, again r = radius
For cone = 1/3πr²h (it's volume is one third of a cylinder of the same height and radius!)
Hope it helps dear friend