"100/500 KBPS" may mean either "100/500 kBps" or "100/500 kbps", which one is it?
kB = kilobytes = 8× kb = kilobit; you can do the math
As for the modem, open up the command prompts (Windows key + R > cmd.exe) and type in "ipconfig", you should see something like this:
The "Default Gateway" should be the address of your router/modem and you should type that IP into your browser to access it.