Theory:

Metric units of length (mm, cm, m, km)
Converting large units to smaller units.
\(1 cm = 10 mm\)
\(1 m = 100 cm\)
\(1 m = 1000 mm\)
\(1 km = 1000 m\)
 
Converting smaller units to larger units.
\(1 mm = 1/10 cm\)
\(1 cm = 1/100 m\)
\(1 m = 1/1000 km\)
Metric units of length (kg, g)
Converting kilograms (\(kg\)) to grams (\(g\)).
\(1 kg =1000 gm\)
 
Converting grams (\(g\)) to kilograms (\(kg\)).
\(1 gm = 1/1000 kg\)
Metric units of length (lt, ml)
Converting litres (\(lt\)) to millilitres (\(ml\)).
\(1 lt = 1000 ml\)
 
Converting millilitres to litres
\(1 ml =1/1000 lt\)