Convert from button measure to bicron

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 (bicron)
The Bicron is an obsolete metric unit of distance, which was defined as 10e-12 meter or 10e-6 micron. This distance is now called a picometer or picometre (pm). The name is a reference to the double prefix "micro-micron".