Convert from parasang to X unit

Unit Definition (parasang)
The parasang (Persian - farsang) is an ancient Persian unit of itinerant distance corresponding to approximately 3.5 miles (5.6 kilometers)., or the distance that can be traversed on foot in an hour.

Unit Definition (X unit)
The X-unit (symbol xu) is a unit of length formerly used to measure the wavelength of X-rays and gamma rays. The X-unit is approximately 1.0021×10-13 metre. Defined by the Swedish physicist Karl Manne Georg Siegbahn (1886-1978) in 1925, the X-unit could not at that time be measured directly; the definition was instead made in terms of the spacing between planes of the calcite crystals used in the measuring apparatus.