Don't you mean "cone shaped?"
The formula for the vol. of a cone of base area b and height h is V = (1/3) b h.
Here, you are told that the diameter of the base is 24 feet. Hence, the radius is half that, or 12 feet.
The area of the base is pi times r^2, or 144 pi ft^2; the height is 10 feet.
Multiplying, V = 1440 pi ft^3. Just as an example: The volume, to the nearest 100th cubic foot, is V = 4523.89 cu ft.