Not seeing files on external drives

We had a power failure recently, the server went down,when it came back on could not see files but
the audio program can still access it.
The ext. drive stores the audio file. The server stores the cart file which access the audio files.
When youuse windows explorer to view files, the status is saying 0 ojbects:freespace 29.8GB. I need help, without reformating drive or explain what is happening.