Modems? Thats something I haven't seen for a while
If things haven't changed, which I doubt, I don't think you need a driver for modems.
You should be able to talk to it through the serial ports e.g. COM1 is /dev/ttyS0
To e.g. connect to an internet ISP you can then use PPPd (the Point to Point Protocol deamon) and a chat script.
If you search the net or ask your ISP you might be able to find a script to use. Your modem manual should have some initialization strings to use ("ATZ" might be enough for most cases).