The 3.5mm Toslink cable is usually found on portable CD and Minidisk players or laptops. TV's usually have a 3.5mm analog stereo output. The converter referenced above is digital-to-analog. If the TV output is analog stereo, you would need an analog-to-digital converter. If the TV has a 3.5mm Toslink port, then the cable is all you would need.
Does the sound bar have an analog input (red and white RCA plugs)? What's the make and model of the TV?