Distance units of measurement
When Metric units system is selected its only meters or kilometers that can be used for distance.
For Imperial units system, these are feet and miles.
For Nautical though you can set if these are meters or feet that are used for distance.
Whatever the choice or constraint above is, you can pick when display of meters and feet changes to kilometers and miles (or nautical miles).
Here is how the screen with distance units of measurement looks:
And a bit more on setting up automatic switch from small to big units display:
Switch between small and big units
Area and length units of measurement (planimeter).
General units of measurement - Metric, Imperial, Nautical.