They're both just misfire codes, harmless in themselves if the engine's running smoothly otherwise. Chances are good that you or someone washed or steam cleaned the engine and if so, the spark plug holes might be filled with water which then sets misfire codes.
If there's water in those holes, dry them out and you should be OK. Otherwise check spark plugs if there's doubt on their condition.

Then, clear the codes and drive it for a while. Usually the codes won't re-appear unless there's another problem, like a faulty injector for example (not too common).

Don't worry about the cat.conv either as some might suggest. I have yet to see actual TWC damage to an 850 due to misfire codes.