The basic metric unit is the metre.
meters
The ISO length unit to use would be the cementer.
Meters are used as the unit for length in most countries, but some, such as the United States, use a different system of measurement.
Units of length, such as mm, are used for this.
I would expect it would be centremetres.
It's SI unit is meters
always the meter to measure length. This is an SI (international) unit of measurment, and is the standard international unit of measurment for length.
miles or kilomiters
Kilometers are a unit of length, used to measure distance.
If not use the standard unit, you won't get correct answers when calculating.
The unit of length is metre(m), unit of volume is centimetre cube(c.c), unit of mass is kilogram(kg).
It would be normal to use either meters or feet, but you can use any unit for length (inches, cm, mm, km, etc.)