[amsat-bb] Working ISS and or other digis

I know there are many out there that work the ISS and cube sats . The question is do any of you use Apple Mac's to do so. If you do what are you using ? I have been trying quite unsuccessfully to get a KPC3 that I got back in 97 to talk to the Mac mini using a TRENDnet TU-S9 usb to serial cable. Using MacTNC or Zmodem. They just do not see a serial port to go to. I am thinking of trying an outboard interface like signal link or one of the others with a built in sound card to use digital modes. I am getting very frustrated and not sure which way to go next. So if any of you Mac users could give me a little advice I am open to it. Thanks -73 WB8ZOM Don