Convert from button measure to mille [French]

Unit Definition (button measure)
The button measure is a unit of distance equal to 1/40 inch (0.635 millimeter), used to measure the thickness of buttons.

Unit Definition (mille [French])
The mille is a traditional French mile, equal to 1000 toises. This is equal to about 6394.4 feet, 1.211 statute mile, or 1949 meters. In modern France, the mille sometimes means the nautical mile (mille marin), equal to exactly 1852 meters.