Convert from metric mile to league [ancient Celtic]

Unit Definition (metric mile)
A metric mile is a distance of 1,500 meters. This distance is used when it is desirable to approximate the statute mile, yet also desirable to use a convenient round number in SI or metric units. A statute mile is actually 1,609.347 meters.

Unit Definition (league [ancient Celtic])
League is a unit of distance long common in Europe and Latin America, although no longer an official unit in any nation.