How to write 3 meters, 5 meters and 8 meters?

3dm, 5dm, 8dm. The length meter is represented by the English letter M, the length decimeter is represented by the English letter dM, the length centimeter is represented by the English letter cm, and the length millimeter is represented by the English letter MM. One meter equals ten meters, one meter equals one hundred centimeters, one meter equals one thousand millimeters, one decimeter equals ten centimeters, one decimeter equals one hundred millimeters and one centimeter equals ten millimeters.