Multiply km by 1 million to get mm
Multiply mm by 0.000001
km is bigger than mm km = kilometre and the kilo- prefix means multiply (the unit) by 1000. mm = millimetre and the milli- prefix means multiply (the unit) by 1/1000. x1000 is bigger than x1/1000 so km is bigger than mm.
Multiply by one million.
Multiply km by one million (1km is 1 million mm): 65km = 65 x 1,000,000 = 65,000,000mm
You multiply the number of kilometers by a million.
Multiply by 1000000. So 3.4 * 1000000 = 3400000 milimeters.
en.wikipedia.org/wiki/Earth_radiusfind the radius in km and multiply by 1 million.
2.4 km * 1,000,000 mm/km = 2,400,000 mm
106 mm = 1 km so 36100 mm = 36100/1000000 km = 0.0361 km. Simple!
1,000,000 mm = 1 km
0.000001 km = 1 mm