Assuming you mean the converter, open the cover, read the manufacturer and model number on the label, and check their website, or post back here with the name and numbers. You gave us trailer, but not year, and not all trailers all equal, based on options.
I'll also ask, why do you need to change it? What problem do you have?
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT