JimandSusan, assuming it is working you can sometimes find the converter by listening for its cooling fan. Turn everything off that makes noise and then turn on every item that runs on 12VDC like a bunch of lights including those in your basement compartments and then listen for the cooling fan to come on. If all your lights are LEDs, you may need to turn other things on like vent fans but their noise makes it harder to hear the converter fan. Note this only works if you have 110VAC power to your converter - either shore power or generator. Generator noise will make it harder to hear the converter fan though.
Also, a lot of times Winnebago put them under the refrigerator but not always. Look for a brown metal panel.
2021 Winnebago Vista 35U towing a 2010 Cadillac SRX
2003 Itasca Sunova 30B