Retrieving Files from Western Digital My Book for Mac 2 TB USB 2.0 Desktop External Hard Drive

I’ve been updating my mac on this external harddrive since I bought it in 2012. Something went terribly wrong when I updated my computer to Yosemite and I ended up having to reboot my computer at the Apple Store. When I plugged my external harddrive into my computer today it said that it had half a terabyte on it but all the files are empty. Is there a way I can recover my music/photos/documents/etc.? 

Hello and welcome to the WD Community.

Were you using any specific backup software? or you were you backing up your files manually?

Yes.

Have you tried using some free online software to see if you can see the files? Just search for free data recovery software online. Be careful to not start spending money on useless software unless you can actually see the files that you want to recover!

Good luck.