There seems to be some lack of knowledge of how things are suppose to work and what they are called...
Here is a typical 30AMP Trailer Electrical setup showing how everything works around the 120VAC Power Distribution Panel where the BREAKERS are located and the 12VDC Power Distribution Panel where all of the FUSES are located...
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As you can see here these two panels are the heart of your trailer operations... These two power distribution panels is where every thing in your trailer gets it power from...
The items you are describing for replacement are called an DC Converter (Sometimes called a Power Converter or a Converter/Charger) and its function is to take the Shore Power or Generator 120VAC output and convert it to 12VDC which in turn feeds the 12VDC Power Distribution Panel to power up all of the 12VDC items you see above.
This has nothing to do with the 120VAC Breaker side of the 120VAC Power Distribution panel. When plugged into shore power or running off of generator the Power Converter unit also will become a battery charger for your trailer battery.
Not having any 120VAC around the 120VAC Power Distribution Panel BREAKERS means something is wrong with the Shore Power or Generator connection feeding the trailer. Need to check your 120VAC Input Source...
Totally confused here on what you are wanting to do from your description of events...
Roy Ken