1TB External Hard Drive Lost All Data

I have been using a WD External 1TB to back up a lot of the photos for my photography business and a client that I did work for months ago is being interviewed by a magazine and wants to use my photos for the magazine article.  I plugged my external hard drive in, and it shows all of the root menus and file folders, but when I click to go into any of the folders they are all empty.  I have accessed information off of the hard drive like this in the past, but for some reason now all of the folders are coming up as being empty.  Any help or suggestions would be very much appreciated as this is a devastating loss of information if it indeed has been lost.

Thanks

It sounds to me that your drive might have been infected by a virus.  To get the data back you must first scan your drive for viruses, then use a data recovery software.