you would measure a wall in meters
Meters.
Meters
Not normally because meters would be more appropriate
Ex. the distance between two cities A kilometer is 1,000 meters
you would measure a wall in meters
Kilometers
meters
Meters.
Meters
Meters
Neither. By centimeters
Usually, you would use kilometers.
5160 meters is a measure of distance, not weight. To convert meters to kilometers, you would divide by 1000. So, 5160 meters is equal to 5.16 kilometers.
It really all depends on..... common-sense. You would use metres and decimals thereof. One decimal place is probably near enough for a couch, but note that under SI rules, it would be expressed in metres and millimetres, and as either all mm or N.xxx metres.
milimeters
if you are talking about how tall you are, meters would be the best choice. for instance if you are 2 meters tall (6ft give or take a bit) that would be like .002 kilometers