Front speakers don't work/ may not be connected

Hey guys,

I just bought my 2000 chevy c3500 and when i turn the radio on the front speakers don't
play at all as if they are not connected. I have two questions related to this:

1. Under the passenger side of the seat there are 4 RCA cables coming through the
floor that are not plugged into anything at all and I'm wondering if this the speaker wires
that just need to be connected? If not what are these wires for?

2. I was reading online that the seat belt alarm and the front speakers could be
connected to one another and the seat belt alarm is cut on the drivers seat. Could the
cut wires leading to the seat belt interfere with the front speaker connections?

These are my two best guesses as to what the problem may be but I'm having trouble
finding any information on the audio system for this truck. Also as a side question
where do the front door speaker wires run to get to the radio?

The head unit is an older aftermarket kenwood receiver and what seems strange is that
when I pull it out there are no RCA cables being input to the front and rear speaker
inputs, yet the rear speakers play fine.

Thank you for any help, I really appreciate it.