Unable to Locate Files When Attempting to Transfer Data to New SD Card.

I am attempting to upgrade my SD Card on my 3DS XL.

When I insert my SD Card into the card reader, Winows finds the card yet it says that it must be formatted before opening. I assumed that the Data was corrupted, but upon placing the card back into my 3DS, all of my data is intact and fully functionable.

Is there something that I'm missing in order to find my SD Card Data so that I can place it on a new SD Card?

Thanks in advance.