Hi, and welcome to Vinyl Circle where auditory insanity bliss reign supreme.
You need a tonearm cable that plugs into the bottom of the arm. These are traditionally a five pin female cable with RCA + ground wire on one end and a plug called a 5 pin DIN connector.
Grace arms are unique and need a male connector on the end of the cable. If you go to a shop or on line store that sells tonearm cables, look for a Grace type cable. Before you buy the cable, you need to check if you have enough room underneath for a cable with a straight plug, or if you need a cable that is in an L shape, for a table with little room underneath. The easiest way to check is to turn the table so you have the back facing you on the edge of a support, and look underneath. Look and see where the plug-in part is, in relation to the bottom. Chances are a straight plug will work, but you should check. Don't order an L plug "just in case". You might not have sideways room.
It might be easier to remove the arm from the base to install the cable. I think your arm has 2 fittings in the arm base that allow you to adjust the arm height - physically raise or lower the vertical supporting structure called the pillar. Loosen these fittings and you can remove the entire arm and plugging in the cable is straightforward. Thread the cable through the hole and tighten the fittings.
Don't be shy about asking questions. The only dumb question is one that isn't asked.
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