Convert from millimicron to palm [Britain, Roman minor]

Unit Definition (millimicron)
A unit of metric measurement 1000 millimeters equal one meter, 10 millimeters equal one centimeter, about 25 millimeters is one inch.

Unit Definition (palm [Britain, Roman minor])
A palm, when used as a unit of length, is usually four digits or three inches, i.e. 7.62 cm (for the international inch). The width of an adult human male palm is indeed about 10 centimetres.In English this unit has mostly fallen out of use, as do others based on the human arm: digit (¼ palm), finger (7/24 palm), hand (4/3 palms), shaftment (2 palms), span (3 palms), cubit (6 palms) and ell (15 palms).