The MPS3 board provides 4 serial ports over USB. When the board is powered up and connected to a PC via USB, these ports should be visible in the device manager:
Windows Device Drivers not Installed?
Unfortunately new installations of Windows 10 may not provide the correct device drivers required for the USB UART device on the MPS3 board, causing the serial ports to be unusable and not visible in the device manager.
You can download and install the correct Windows drivers for the serial device on MPS3 from here