1 micro is exactly 1 x 10-6 meters. Meters are SI units.
1 Mile is exactly 1.609344 kilometres by international agreement in 1959. In SI units it is exactly 1609.344 meters. The length is based originally on the distance marched in 1000 paces of two steps each. 1mi = 1.609344 km = 80 chains = 5280 ft = 1760 yd.