Okay - this is tough because it depends on how you are connecting on your PC side and how you are connecting on your PLC side, and new products get added and things change, but here's a general summary.
Generally speaking this can be simplified:
If you are on a PLC from the last 5-10 years (it's 2020 now) then mini-USB is probably available on the PLC, if mini-USB is not available, then Ethernet is with the exception of the FX3U and the Alpha. So this includes FX3S, FX3G, L Series, Q Series and R Series released in the last 10 years
If you are working with an FX1S, FX1N, FX2N