reading micro SD card directly from PC
It would be very useful, but afaik this is not possible, since the Arduino sketch you write communicates to the PC via the serial interface only.

The IDE/Arduino driver can use the USB to write your sketch and use the USB for communicating, but for sketches the USB (as direct medium) is not possible.

The SD card will not show up as a specific drive/map/folder on your PC.

Since you want to read the SD card, write in your sketch code to transmit the file(s) you want to send to the PC, to transfer them by UART, and on the PC write a program that reads the serial port and processes it.