You could use square kilometers (km²) or square miles (mi²) to measure the area of Britain.
You could measure a small area.
Square kilometers is a unit of area. You don't run "square kilometers", simply meters, kilometers, etc.
Any non-square unit of length, for example miles, kilometres, millimetres, chains, fathoms, leagues, pounds, kilograms, gallons, degrees. It could be measured in square miles, square kilometres, square millimetres, acres, ares, etc.
You can measure kilometres in metres, which would be 1000, or decametres, that would be 100, or in hectometres, that's 10. You could even measure in decimetres
You could measure pressure in pounds per square inch.
A field has an area. The metric SI unit for measuring area of land is the hectare (a metric unit of square measure, equal to 100 ares (2.471 acres or 10,000 square metres). For very big farms like cattle ranches square kilometres (instead of square miles_ would wok just fine You could measure the length or sides of the field in meters
I think it is reasonable to assume you mean acres however this question can not be answered because it doesn't make sense. You can not compare an acre with a kilometre because they are not measurements of the same thing. A kilometre is a one dimensional measurement, so for example we can measure a line and say it is 1km long. An acre, however, is a two dimensional measurement and can not be used to measure something, such as a line, which is only one dimensional. You can not equate one with the other. Instead you can compare an acre with square kilometres as this too is a two dimensional measurement. An acre is about equal to about 0.004 square kilometres (accurate to 3 decimal places only) and you could fit about 247 acres in a square kilometre.
You could fit 5 full Irelands into Spain, with lots of space left over. Spain is about 5.97 times bigger than Ireland. It is about 504,675 square kilometres. Ireland is about 84,421 square kilometres.
A unit could be anything to a square unit to maybe a 50 by 50 by 2 block. So a unit is anything that can be used to measure an amount of something.
It is an area equivalent to 25.9 square kilometres, approx. The area could be in the form of any 2-dimensional closed shape.
You could fit 7 full Irelands into France, with some space left over. France is about 7.6 times bigger than Ireland. It is about 640,679 square kilometres. Ireland is about 84,421 square kilometres.