sd card is suddenly not recognized - urgent assistance

Hi,

I know how to get to cmd window, I tried that as i saw it on the net, somewhere… but i am not sure for the correct command text, if the sd card in Drive G, is the correct text is : CHKDSK:G    ?

i also found the SD card in the “Device Manager” under portable devices  :G , I checked the window of update over there and it noted that it is updated and works fine so i dont know how to move on from there…

Thanks for your Assistance,