when you say it's a 3 channel set do you mean it's one of the ones with the steering wheel? If it is then you'll need one of the surface receivers such as the sr300. If by chance it's a dx3.0 then they will work fine with it.

You can pick them up quite easily (ebay is about £30) as they seem to still make the ground dsm stuff not like the AR6000 or BR6000.