Code for detecting available sd card devices is working for windows phone 8.1 but not for windows desktop 8.1

I have a usb modem in which sd card is there. I am trying to write a code which detects that sd card .

StorageFolder externalDevices = Windows.Storage.KnownFolders.RemovableDevices;

// Get the first child folder, which represents the SD card.

StorageFolder sdCard =(await externalDevices.GetFolderAsync()).FirstorDefault();

In the above code, error is coming at 2 places. In the 1st line, Windows.Storage is giving error and in the 4th line, FirstorDefault is giving error. This is working fine for windows phone 8.1. Please give ur suggestions to let this code work for windows 8.1 too.