type as root in a terminal. lsusb. this will show your device then type dmesg and this will show your device and the port it will be asociated with. most likely
/dev/usb/ttyUSB0 or /dev/ttyUSBO etc etc
any way ubuntu should find start you gnome gppp or if kde kppp and configure it to use your modem. that said if you are trying to uses the usb wireless modem then please state that.