They are meters to measure
meters.
I would use my legs, not a measurement! To measure the distance, I would use metres.
Miles
you would use kilometers.
A cloth tape measure.
the measurer
To measure the distance of stars you have to measure by light years.
You would typically use miles to measure the distance from Dallas, Texas to Memphis, Tennessee.
I would use the odometer on my car. If that does not help I would use a map and a ruler and measure it to scale.
You would measure the distance of the door with meters because liters measure volume not length.
Light Years.