All versions of Linux have a terminal--it just is sometimes called something else. Look in all your menus for "terminal", "console", or something similar. It's there---trust us.
Another method is to enter ctrl-alt-F1 (or maybe F2 or F3). This will put you in terminal (command-line) mode.
Is the modem a device that connects to the cell phone network? (Not if it is really going to a satellite.) Also, who is the ISP (Internet Service Provider) that provides the connection?
Finally, this Google search has lots of info, including a Ubuntu discussion: