My Book Essentials Edition 2.0 (l TB )

I posted all my pictures and a few other things last night and today the whole thing is gone. Does not even look like I ever had it on my computer.  I really don’t want to loose my stuff. But how do I fix this?  Or has the drive gone bad. It’s only a few months old and this has never happened before.

I may have lost 20 gigs. I just read where it has to be formatted for windows (?) , that out of the box it’s formatted for apple.