The Modbus Plus specification states that the following Modicon parts are to be used when wiring a Modbus plus network.
AS-MBKT-085: This connector is used for inline Modbus Plus device connections. If your ProSoft of ProLinx module is going to be a drop in the middle of a Modbus Plus network, then use this Modicon connector.
MBKT-185: This connector is used for end point Modbus Plus device connections. If your ProSoft or ProLinx module is going to be at the end of your Modbus Plus network, then use this Modicon connector.
490NAA271XX: This is the Modicon part number for the cable required for a Modbus Plus network. The last two digits depend on the distance requirements of your network.
A standard DB9-M type serial connector cannot be used in a Modbus Plus network.