Wrong Router Connection Plug.

[flobadob]

Someone gave me a TP-LINK TD-W896ON router as our current router is constantly needing to be turned off and on again to connect to it. However the input on the back of the router does not accept the connection cable coming from my internet dish ie it's a dish not a phone line.
We have a dish on the roof from which a cable comes into the house, this cable then goes into a little black box called a switching mode power supply and another cable comes from the black box into the router. All of these connectors are the same size.
The input into the new router however is to narrow to accept the current cables we are using. There is a cable which came with the new router which connects to the input of the router, called Line, and it also connects to the black box. But when I connect this up I am not getting an Internet connection. Is there an adapter that converts the larger fitting which I have in my current cable set up that will let me connect to this router?
Sorry for not knowing the specific names of the fittings but I figure anyone who hazards a go at this will know what I mean anyway. Thanks.