HI,
Actually in short "you NEED A MODEM;"
In order to connect your router you need to connect a modem in "bridge mode'( bridge mode is nothing but a configuration on the modem)..
this is a picture of rear side of a router,,, you have to connect the modem into the wan port of the router (above),, and in port number 1,2,3,4 you can connect your computers,
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