As I said, that's not enough information. That could be a DishPro Twin, A DishPro Plus Twin, or a Dish Quad LNB for all you've said. Each of those models has slightly different wiring requirements.
Look at the sticker on the LNB I linked. Does yours have the same sticker? If that's the sticker you have, then it only takes one cable and a separator. If yours doesn't have the same sticker, buy one that has the right sticker; it makes life easier.