Dell Venue Pro Windows 8.1 USB to 9 Pin

I work for a agriculture gps company, and i have a customer with a dell venue pro on windows 8.1.  Im trying to send gps to a farmworks mobile program on the tablet and i have to go through a 9 pin connection.  I have my micro usb to usb, then have a usb to 9 pin (TU-S9) from trendnet and i used the driver they gave me to try and put on there but i dont think it is compatible with the venue pro and the operating system.  does dell make its own usb to 9 pin that would work with this or is there some usb to 9 pin that would be compatible?  

Thanks