I don't understand what you are saying. We need to agree on some terms or I think we will get nowhere.
On this side of the pond (U.S.) a plug is the male gendered part that goes into a hole. That hole is the jack, or female part. I have been told by some people that it is the opposite in England however I have never seen it differ from the U.S. convention at European electronics parts house catalogs.
So, if your speakers have two RCA Jacks, whether they are on a panel or on the end of a cable, you need a cable that has two plugs to plug into them. The other end of that cable needs a 1/8 inch stereo phone plug that will plug into the phone jack which is on the left side of the MacBook. The cable should not have any resistors or transformers or anything else in it, just plain wire.
This all assumes that your speakers want to see a 'line level' audio signal. That is the signal that the MacBook puts out.