"SD card is blank or has unsupported filesystems" message in Samsung Galaxy S4

My Samsung Galaxy S4 showed "SD card is blank or has unsupported filesystems". It then gave me the option to format my SD card, to which I reluctantly consented. After having done so however, it proceeds to present me with the same message, "Blank SD card", regardless of how many times I insist in formatting. After searching on Internet, I found that apparently I should format the SD card from my computer. I don't have an adapter for microSD cards, so I connected my phone with a USB cable to my computer, and apparently my SD card refuses to show up there. Also, for your information, it seems that neither my phone wants to recognize the SD card, for example if I try to transfer apps to my SD card my phone tells me I don't have a SD card. So, is there anything I can do to resolve this issue? Should I buy a microSD adapter and hope that my computer will recognize the SD card then, or should I just buy a new SD card? Or is there something else I can do?