It's a old receiver and probably an older TV. The receiver doesn't have HDMI, so that means the coax optical out from the TV and into the receiver is the only option. It will be a RCA style plug with a yellow inside usually.
As suggested above the TV has coax digital audio output and the receiver has coax digital input. You can use most any coax cable to connect them such as a composite video cable.
You may have to turn the output on, the TV speakers off, and change the audio output to bitstream in the TV menu.
You may have to assige the digital input to an input name in the receiver input set up menu.
Check the owners manuals.