Note: "km2" means (km)2, square kilometre or kilometre squared, and not k(m2), kilo–square metre. For example, 3 km2 is equal to 3×(1,000m)2 = 3,000,000 m2, not 3,000 m2.
A hectare (104 m2) is less than a square kilometre which is less than a square megametre (1012 m2).
The ISO symbol "km²" means "square kilometres" (not to be confused with "kilometres squared"). One of them contains 100 ha (hectares) and/or 1 million square metres (m²) and is a little over twice the size of Vatican City, just over half the size of Monaco (country ranked 192nd by area), and one-third of the size of the City of London.
The Imperial unit "square mile" contains approximately 2.5900 km².