public IList<DisplayUnitFormat> GetAvailableLocationUnitFormats()

//var map = MapView.Active.Map;
//Must be on the QueuedTask.Run()

//Linear location unit formats are not included if the map sr
//is geographic.
var loc_units = map.GetAvailableLocationUnitFormats();

var mv = MapView.Active;
var map = mv.Map;

QueuedTask.Run(() =>
{
  //Get the list of available location unit formats
  //for the current map
  var loc_units = map.GetAvailableLocationUnitFormats();

  //arbitrarily use the last unit in the list
  map.SetLocationUnitFormat(loc_units.Last());
});