Onkyo TX-SR304 Cable problem

[stcharles]

I'm new at this and have an older Onkyo TX-SR304 receiver. I just got a used powered sub woofer with a sound bar connected and DIGITAL inputs. The online user manual for the receiver doesn't say what king of output the woofer has, analog or digital. and I know nothing about this kind of thing. The connection is orange like an RCA connection. My TV has the same connection that's marked "Digital Output (Coaxial)" I need to know what kind of cable to buy to connect from the receiver to the sub woofer if I can. I'd appreciate any help. I'm a novice. Thanks