Norton 360 Backup Issue

I have Norton 360 and have accomplished one successful backup in the beginning onto an external hard drive since my files are too large for the online site. However, when I tried to backup files recently, it appears that all the files are put into .db folders instead of into the 360 backup files and I'm at a loss on what to do.

Can you explain what the @db files are and how I can correct my backup settings to make sure I backup correctly? Also, can these .db files be successfully removed from my external drive?

Thanks for the site - hope to get an answer since I could not seem to get the answer at the Norton site.

Any help is greatly appreciated (since I'm quite a novice at this).