"From what I can tell, there was a red white and blue wire that connected to the old power converter. It must have been doing something since now nothing works after I disconnected it. The black and white wire were the only other wires I disconnected from..."
From that it is likely the old converter was a Magnetek/Parallax 63XX type, which is different in some ways from a modern type. To do this right please provide the model/brand of the new converter you are trying to install.
Meanwhile, you need 120v to the converter which you have via the black and white input wires. The output wires go to a DC fuse panel, which has all the fuses for the various 12v circuits you want working.
The battery also connects to this fuse panel which will have set-screw lugs for the pos and neg battery wires.
The 63XX converter has three 12v output wires going to its fuse panel. red and blue are both pos, and the white is the neg.
The 63XX model has dirty 12v output which is ok for lights and fans but not for electronics. So the battery is required to be connected to run the electronics circuits to be a filter so they get clean 12v.
The battery itself provides clean 12v so all circuits can be run from it when off-grid. Modern converters also provide clean 12v so they do not need any battery to act as a filter, and their fuse panels are not split. So they have two output wires, neg and pos. White is neg and often blue is pos. You can use the old split panel if there, but you must jumper the two pos lugs where the red and blue go, and then put the one pos output wire on the new converter to one of those lugs.
You need to organize a fuse panel to get your newer converter working to supply the 12v circuits. You need a battery to run them off grid.
There are units you can buy that have the whole power centre to them, which include an AC breaker panel, a DC fuse panel, and a converter, if your rig no longer has these.
https://powermaxconverters.com/product/ppc-series-draft/Here is a link with some photos showing some of these things mentioned above where a guy replaced his 6300 with a different converter, to give you some idea what is involved. But the detail for your own situation will be different depending on which model of converter you got and what is still left in the rig after the PO's efforts.
https://www.bestconverter.com/Magnetek-Upgrade_ep_26-1.html
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.