How to set up the communication port of Mitsubishi PLC programming software? I just set up the COM number. I just bought a Mitsubishi PLC program download line USB interface.

You should check the port number of your USB programming cable that is visualized in the port of the hardware manager, such as COM8, then set it to COM8 in the programming software.
In general, COM4 or above will be visualized on the notebook, and COM6 or above will be visualized on the desktop.