None.
A millimetre is a measure of length in 1-dimensional space while a square kilometre is a measure of area in 2-dimensional space. The two measure different things and, according to basic principles of dimensional analysis, any attempt at conversion from one to the other is fundamentally flawed.
0.25 km = 250,000 mm
1 km = 1,000 m = 100,000 cm = 1,000,000 mm1 km^2 = 1,000,000,000,000 mm^2 or 10 ^12 mm^210.8 km^2 = 10.8 x 10 ^12 = 1.08 x 10^13 mm^2(10,800,000,000,000 mm^2)
1 mm= 1/1000 km
10000 mm = 0.01 km
4.3 mm is equal to 0.0000043 km
8490 mm = 0.00849 km
25.6 kilometers (mm / 1,000,000 = km)
To convert from mm to km, divide by a million.
6,000,000 millimeters = 6 km
1,000,000 mm = 1 km
1000 mm = 1 m = 0.001 km
6,000,000 mm