Without makes and model numbers a precise answer is not possible.
In general most new TVs have an optical digital audio output. If you old surround sound doesn't have optical in then you can use a DAC to convert to RCA analog audio http/www.parts-express.com/parts-express-dac-digital-to-analog-converter-%2851-compatible%29--180-999
If your TV has a headphone jack then a cable with a 3.5mm stereo plug at one end and 2 RCA plugs are the other end will work.
Without makes and model numbers a precise answer is not possible.
In general most new TVs have an optical digital audio output. If you old surround sound doesn't have optical in then you can use a DAC to convert to RCA analog audio http/www.parts-express.com/parts-express-dac-digital-to-analog-converter-%2851-compatible%29--180-999
If your TV has a headphone jack then a cable with a 3.5mm stereo plug at one end and 2 RCA plugs are the other end will work.