There are numbers of units for measurement of length/distance e.g. centimeter, millimeter, kilometer etc. And many times we got confused how to convert one unit into other.
So lets clear this confusion :
Read Table  1 :
10 Millimeter (mm)  =  1 Centimeter (cm)  10 Centimeter (cm)  =  1Decimeter (dm)  10 Decimeter (dm)  =  1 Meter (m)  10 Meter (m)  =  1 Decameter (dam)  10 Decameter (dam)  =  1 Hectometer (hm)  10Hectometer (hm)  =  1 Kilometer (km) 
From table1, we understand that Millimeter is the smallest and kilometer is largest units of measurement (most commonly used) and assign 10 units to every level and we get Table  2:
Units of Measurement(smallest to largest)  Short name  Levels  Millimeter  mm  1  Centimeter  cm  2  Decimeter  dm  3  Meter  m  4  Decameter  dam  5  Hectometer  hm  6  Kilometer  km  7 
Now, if, conversion of units involves going up to down (as per above levels) then divide the given number by 10^{number of level going down}
Consider following examples to under this :
Example 1 = Covert 5 millimeter into centimeter
Answer = Since this conversion involved going down by one level (as per table  2), so the given number will be divided by (10)^{1} and we get
5 millimeter = 5 / 10 centimeter = 0.5 cm
Example 2 = Covert 150 centimeter into meters.
Answer = Since this conversion involved going down by two levels (as per table  2), so the given number will be divided by (10)^{2} and we get
150 centimeter = 150 / (10)2 meter = 150 / 100 m = 1.5 m
Example 3 = Covert 9432 meters into kilometer
Answer = Since this conversion involved going down by three levels (as per table  2), so the given number will be divided by (10)^{3} and we get
9432 meters = 9432 / (10)3 kilometer = 9432 / 1000 km = 9.432 km
And, if, conversion of units involves going down to up (as per above levels) then the given number will be multiplied with 10^{number of level going up}
Consider following examples to under this :
Example 1 = Covert 5 kilometer into centimeter
Answer = Since this conversion involved going up by five levels (as per table  2), so the given number will be multiplied with (10)^{5} and we get
5 kilometer = 5 X 100000 centimeter = 500,000 cm
Example 2 = Covert 10 decameter into decimeter
Answer = Since this conversion involved going up by two levels (as per table  2), so the given number will be multiplied with (10)^{2} and we get
10 decameter = 10 X 100 decimeter = 1000 dm
Example 3 = Covert 2 meter into millimeter
Answer = Since this conversion involved going up by three levels (as per table  2), so the given number will be multiplied with (10)^{3} and we get
2 meter = 2 X 1000 millimeter = 2000 mm

