by saying the number with a 3 above it
Some units are the cubic meter, the cubic decimeter (= liter) and the cubic centimeter (= milliliter).
liter and cubic centimeter
liter and cubic centimeter
liter and cubic centimeter
cubic or cubed
Commonly used units include cubic meters, cubic decimeters (equal to liters), cubic centimeters (equal to milliliters).
cubic measures such as cubic feet, cubic meters
cubic centimetres, litres, cubic metres.
From your question, it is difficult to determine why you can express the volume of a 12-sided object in cubic units. We do not know the measurements or method to which you are referring.
Cubic meter; cubic kilometer; liter (= cubic decimeter), milliliter (= cubic centimeter), cubic millimeter...
You would use the cubic meter (m^3) to express the volume of a textbook in SI units.
The most common units used to express the volume of gas are liters (L) and cubic meters (m³). Other units such as milliliters (mL) and cubic centimeters (cm³) are also used for smaller volumes.