You can probably write a script to convert one type to another. But honestly, I have always said, do all of your material work inside of Omniverse. Just get the raw geometry in and then apply new, fresh materials in Omniverse. Much easier that worrying about converting materials. If you want to make some simple “holding materials” in 3dsmax, just to make it easy for selection, you can do that as well. For example, if you have less that 50 parts, maybe not worth it. But if you had 1000 parts, if might be worth applying a material just to give your that selection in Omniverse, that you can easily swap out.
So
“metal” >>> “shiny_aluminium”