Convert from gnat's eye to millimeter

Unit Definition (gnat's eye)
The gnat's eye is an idiomatic "unit" of distance; it's common to hear that something is "as small as a gnat's eye". In fact, the eyes of typical gnats tend to have diameters similar in size to a hair's breadth: roughly 100-150 micrometers (0.10-0.15 millimeters).

Unit Definition (millimeter)
The millimeter (or millimetre) is one of the most common metric units of distance. One millimeter is exactly one thousandth of a meter. The millimeter is also an engineering standard unit.