The formula for the volume of a cone is V = (1/3) b h, where b is the area of the base and h is the height. If the diameter of the base is 6 m, then the radius is 3 m and the area is 9 pi m^2.
Multiply this result by the height, 7 meters: V = (9 pi m^2) (7 m) = 63 pi m^3.