RJ45 modem slot

I have Atlantic Broadband cable broadband. The modem is a Motorola Surfboard model SB5101. It is connected to my computer via Ethernet socket. It also has a USB socket. I bought a Monoprice wireless-N router. The router connects to modem via an RJ45 cable connected from router WAN to modem. There is no RJ45 socket to connect the other end to broadband cable modem. What brand, kind of cable modem must I buy? Also my Ethernet connection keeps falling out of the modem. Do I need a new one? :cry I am frustrated beyond belief. All I want to do is get Net-flex via ROKU on my TV in the next room. Oh, Router is 300Mbps. Any help will be appreciated.

 

"The router connects to modem via an RJ45 cable connected from router WAN to modem. There is no RJ45 socket to connect the other end to broadband cable modem. What brand, kind of cable modem must I buy?"

The RJ45 cable plug is narrower that the Ethernet socket on Modem and too wide to fit into the USB socket. Are you saying that an Ethernet cable and a RJ45 Cat5 patch cable that came with the router to connect (per instructions) are interchangeable?

I am connecting the computer Ethernet to one of the 4 LAN slots on the router. But I can't connect the router to modem with the RJ45 provided. is the modem the problem? do I need a modem with both Ethernet and RJ45 slots?????
Thanks for your help.

 

Okay, everyone missed the point on this. If the router has a RJ-45/etheret connection, that the he first thing that needs to be done, is that the OP needs a router/switch or router including wifi to allow them to share the ISP connection.

 

Am only using 1 computer. Computer connects to router via Ethernet to 1 of 4 Ethernet slots in back of router. The router is then supposed to connect to the modem via RJ45(not Ethernet) from the blue WAN to the modem. The problem is the RJ45 cable (provided) will not fit in the Modem's Ethernet slot nor it's USB slot. Do I need a different modem that has a RJ45 slot instead of an Ethernet slot ? My current modem is a rental from the cable company.

The second choice on your reply is mine, with the 2 antenna.
Thank you for sticking with me.

 

Thank you. My son was able to connect the RJ45 from router to modem. We still cannot get the router recognized by modem/computer. Think I will just get a new computer as this one is from 2002 and only has 256 RAM. Does that seem like a good idea?
Also would I be able to transfer my pics etc from windows XP-32 bit into Windows 7 64 bit? Do I need special equipment for that?

Thanks you have been very helpful and I appreciate your patience.

 

This may help.

When you add the Router inline between the Cable Modem and the Computer, you MUST restart the Cable Modem so it will recognize the Router. To restart thr Modem, Unplug the power cord to it and the Router. Start only the Modem and allow it to boot, about 45 seconds. Then start the Router. The start the computer.