Kk, it should have a network plug on the modem then, you can either use inet sharing from pc, or run a network cable from the modem into ps3...
Keep in mind if you're using inet sharing you might need to configure your router (modem) to let the ps3 have full access to the net with no firewall... also sometimes called DMZ (demilitarised zone?) in settings, as it will need a fair ammount of ports to be open for things like voice chat etc... even moreso for games like eye of judgment (as it uses video)... if you have major issues, pm me and I'll try to help out with precise settings... don't bother ringing bigpond as they won't support it...