I guess liters or gallons..I have the question too, and this is what I am answering.
Litres
gallons
cm³ (cm cubed)
Length would be the most appropriate unit of measurement
centimeters are a small unit of measurement. Pools are very large. You would use it on a fish tank.
Cubic yards.
mililiters
Cubic centimetres.
A ruler. Measure one of the sides, and take that measurement times itself three times, and you'll have the volume.
volume= length times width times hight.
Probably a cubic centimetre.
I wiil use water
gallons
You can not measure the volume of a liquid with a measurement designed to determine length. A centiliter is a measurement of volume, or the amount of space that a liquid can consume inside an object. A centimeter, would be a measurement of length and a centigram is a measurement of mass (weight).
Each side would measure 7 centimetres.
cm³ (cm cubed)
It matters what you are trying to measure. For instance the largest for distance would be different than for volume.
Many units are used to measure volume; in SI, the basic unit would be cubic meters, since lengths are measured in meters.