Try using a bit of common sense, shall we?
5 mm is less than half the width of a finger.
5 cm is about the length of a finger
5 dm is about the length of your forearm (and hand)
5 m is about three times as long as you are tall.
Now see if you can work out which is the most appropriate.
Meters
length would be about 1dm, but dms are not used. centimetres would be more mainstream to use
The answer depends on what you wish to measure: its length (or width or height), its mass, it fuel efficiency, it maximum speed, its maximum acceleration, its tightest turning circle, its power output, its drag, etc.
The RMS Titanic was approximately 104 feet (32 meters) tall from the keel to the top of the bridge, while its length was about 882 feet (269 meters). This means the difference between its length and height was around 778 feet (237 meters). The Titanic's impressive dimensions contributed to its status as one of the largest and most luxurious ocean liners of its time.
A tape measure that measure in feet and inches (or meters and centimeters) would be most appropriate.
kilometers
It depends on what you're measuring it for. You could be testing it for the following measurements: Height (using meters would be the most appropriate). Length (using meters would be the most appropriate, kilometres if long enough) Mass (tonnes would be the most appropriate). Volume (m3 would be the most appropriate). Area (m2 would be the most appropriate). Time taken to cross (depends on the length of the bridge. Minutes and seconds would be appropriate).
Meters
Any measure of length will do, but the most common would be feet or meters.
Grams is no good - it is a measure of weight not length. Kilometers measure length - but only if your table-top is a few miles long. Most appropriate would be Meters - your average dining table is about one-and-a-half meters long.
Metres.
A standard skateboard is typically about 78 to 84 centimeters long, which is equivalent to approximately 31 to 33 inches. The exact length can vary based on the type of skateboard, such as a cruiser or a longboard, which may be longer. Most skateboards have a width of around 20 to 23 centimeters.
The most appropriate SI unit for measuring the length of an automobile is meters (m).
TESTOSTERONE
length would be about 1dm, but dms are not used. centimetres would be more mainstream to use
Meters
Most UTP cable is limited to 100 meters.