I got my receiver, hitch and converter from U-Haul. Good prices on good products.
Since I have a 2001 and the discussion is about a 1998, I'd imagine some differences were involved, although Volvo doesn't change dramatically over time.
The converter comes complete with a length of heavy gauge wire and fuse holder to power the converter whether the battery is in front or back.
The part #13493 is about $40. The converter also has test lights built in so you can tell a source problem from a trailer problem. The converter is fed by ground, battery+, stop, L turn, R turn, tail. You can fish the 4-flat through a grommet on the rear or just toss it out the tailgate. The salt here in Michigan eats up the connections, so I keep it all 'inside' when not in use.
I don't know which connections were which without testing with my test light.
Everyone needs a test light in their bag of tricks.
Ed