The built in serial ports on a CompactRIO (cRIO) will show up under VISA resources as ASRL1:INSTR, ASRL2:INSTR,
... by default. This is the correct behavior, and if you select the corresponding port, it will use that port as the VISA resource. You can see the serial port naming under Remote Systems >> Name-of-your-cRIO >> Devices and Interfaces
and you can give a name to the serial port under Settings
as shown in the image below. This is where you can give the port a name of COM0
if you would rather refer to your serial ports with those names.