The convention for D-subminiature connectors such as the ones we're talking about is to show (and install) them with the longer row of contacts on top (opposite of yours); looking at the male (pins) connector the numbers start at the top left, the female side as used on the M100 etc. thus starts at the top right. Since we're talking about pins 2 and 3 they're the same location on both DB-25 and DE-9 connectors.
M100 (female) pinout: DE-9 (AKA DB-9) male pinout
