Miles or kilometers.
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.
mm, or possibly cm
length would be about 1dm, but dms are not used. centimetres would be more mainstream to use
Any measure of length will do, but the most common would be feet or meters.
By unit of length and distance and conversion ,we can say that the most appropriate unit to measure the length of a finger is cm.
The most best unit to measure the length of a slice of pizza are inches.
Metres would be the best unit to measure the length of a backyard