Your Sony only has analog audio RCA inputs. If you cable box is the only source then use the RCA audio outputs on the cable box directly to the Sony. A stereo RCA cable is all you need.
If you have other sources then it would be easiest to get the audio from your TV.
If your TV has a headphone jack or RCA audio outputs (not inputs) then use them.
If your TV has an optical audio output then you will need an optical to analog converter like this one
https
/www.amazon.com/Digital-Optical-Analog-audio-converter/dp/B004C4WPXA
You may have to turn the optical audio on, the TV speakers off, and set the audio to PCM in the TV menu. Will depend on the TV.