I bought a dryer that was converted to propane gas. There were 2 orifices that came with the dryer to convert it back to natural gas. I was wondering which one I need to use to do this. One orifice has a hole coming from top to bottom. The other has a hole coming from the side to the bottom. Maybe I need to use both to convert it, in which case I don't know where they go.

Be careful please, I am no expert but the propane gas orifice has a tiny tiny opening, and the natural gas dryer, a smaller opening. (most new gas dryers come from the manufacturer setup to handle natural gas, then can later be adapted to propane by using the orifices supplied normally with the new natural gas dryer). Anyway, be careful, wish I could help on the orifices but not qualified, any doubts I suggest you call a pro.

If you want to do this yourself I recommend this:

Call the manufacterer of the dryer, request a OEM part number for the orfice of the gas type you want to run, then compare the part number you have. If they do not match, discard the orfices you have and order the correct orfice from the factory.

Converting back to natural gas is not only a matter of replacing the orifice. There is another piece that needs to be changed. I think it is a vent which is in the same area, but not sure.