There are non sound decoders that just control motor functions. SOme are hardwired into the locomotive, some plug into a socket on the PC board. Both these non sound decoders and the sound versions are called mobile decoders. DO not confuse these with accessory or stationary decoders. A mobile decode is what you want for the turntable.
I assume by the turntable length you are running N scale. The only instruction sheet I could find on the Bachmann website is for the larger HO scale version, but it may provide some guidance. It looks like the decoder is a plug in version, and if this is also true of your turntable, and mobile decoder with an 8 pin plug will do the job.
https://shop.bachmanntrains.com/documents/46298_HODCC-Turntable.pdf
I assume by the turntable length you are running N scale. The only instruction sheet I could find on the Bachmann website is for the larger HO scale version, but it may provide some guidance. It looks like the decoder is a plug in version, and if this is also true of your turntable, and mobile decoder with an 8 pin plug will do the job.
https://shop.bachmanntrains.com/documents/46298_HODCC-Turntable.pdf