Finding cubic meters is the same thing as finding the volume of an item, measured in meters. Take a few measurements, do a simple calculation, and you have your answer. Just grab your metric ruler and use the formula H(eight) x L(ength) x W(idth) to determine the cubic meters of any item.
One cubic meter is the same as 1,000 liters, 35.3 cubic feet and 1.3 cubic yards.
Measure the height of your object and record it on a piece of paper.
Measure the length of the object and record this number, as well.
Measure the width and write this number down.
Multiply the three measurements. The answer is given in cubic meters. For example, if the height of your object was 12 meters, the length was 6 meters and the width was 2 meters, you would multiply 12 times 6 times 2 to get 144 cubic meters.
TL;DR (Too Long; Didn't Read)
Convert measurements to meters if they are not already. If measurement was taken in millimeters, divide by 1,000. If by centimeters, divide by 100. If all you have is a standard ruler, convert feet to meters by multiplying the measurement in feet by 0.3048.