The basic unit of the metric system is the metre. Its subdivisions are the decimetre or 1 dm (rarely used) which is 1/10 of a metre; next is the centimetre or cm, 1 cm = 100th of a metre or .01 m; 1/10th of a cm (or 1/1000th of a metre) is a millimetre, 1 mm. Going up the way, 10 m = 1 Decametre, or 1 Dm (rarely used), then 100 m is 1 Hectomatre or 1 Hm (rarely used) and finally 1000 metres = 1 kilometre or 1 km. As you can see the whole system is based on multiples of 10.
Retired Maths Teacher