Question on wiring for 2010 model 622 Trailer. The trailer is wired with the original 9 pin round plug, and I have a 2014 RTL with the factory hitch and 4 wire square plug. What is the best way to convert the 9 pin on trailer to 4 wire square or flat? I've read various articles and I'm confused about the amber back-up lights on trailer. Thanks in advanced for everyone's input.