If that does not work, try Recuva
. But first I would try diskpart. Open an elevated command prompt ( click start, type cmd in the dearch box, right click on cmd and select run as administrator) In the box that comes up, type diskpart, press enter and in a few seconds the window will respond by saying diskpart. Type list disk and it will list all disks connected to your computer. type select disk # (where # is the number of the disk you are having issues with). press enter. it will respond with disk # is the selected disk. Type assign and press enter. If this works, it will assign it a drive letter. Type exit and press enter twice to close the window.In that case you can open it with explorer and look at the files inside.