You'll need cables to connect your plotter to your computer. If you have an older plotter you probably have a parallel port at the back, but your computer doesn't have such a port, they stopped putting the on computers about 10 years ago! So now we know that you need a parallel to USB cable -- BUT it must be a BI-DIRECTIONAL cable so that the computer and plotter can continue to communicate in a big circle throughout the printing. Do not buy the cable at the local big box store UNLESS it says in the details that it is BI-DIRECTIONAL -- if it doesn't say it in the bullet point features on the package, it generally isn't. Here's the ones I keep in stock at my workshop! The first is 16 ft. long and the second is 6 ft long.
6 ft usb to parallel port cable (Bi-directional)
extension cable (bi-directional) 12 ft usb to parallel cable
If your plotter has a network adapter you can tell by the outlet that looks similar to a modular phone jack, but a bit bigger. These are preferred by folks who want to put their plotter in a separate room because you can use a cable that is a hundred feet long, or more. The cable is a CAT 5 or CAT 6 cable. Here's a flat 100 foot CAT 6 cable:
Do no use USB Hubs (just one shown above) as they will often disturb the bi-directionality that is a requirement with these large format printers. If you try them and they work, great...but it is the weakest link and the most often suspected if you are having trouble getting your prints out of the print queue and onto the plotter!