How to verify game files

I hope this is in the right section. In the last update I managed somehow to loose some custom sound files. I got those back and in the mean time I lost the horn on my Dash 9. I know that I screwed that up. I am currently in offline mode. I need to go to on line mode and verify my game files. How do I do that? I know that there is a batch file to hold all of my custom sounds as back up. I do not know how to use it and I am kind of on my own on this one. No one to help me with it. I am afraid of loosing my custom sounds when I go back into on line mode, and getting them back to were they need to be is about a half day ordeal for me. Is my best bet to leave it alone? I miss my Dash 9's. Please keep it simple. I have VERY limited knowledge of this kind of stuff.