dmtaurus,
Surface roughness units are either in micrometers or microinches, and the units should be stated along with the required value. ISO and DIN are metric, ANSI is inch, not sure about JIS. The conversion factor is the same as that between meters and inches i.e. if roughness is given as 3.2 micrometers, you multiply this by 39.37 to obtain microinches (= 125)