My personal bookmarks have disappeared.

Three days ago a window popped up asking me to update Firefox. I did and afterwards my personal bookmarks listing disappeared. I tried rebooting everything. No luck. I went to your website and followed all of your suggestions, but again nothing worked; mainly because I could not find on my computer the info the last step in your suggestions were asking for. (I did get a message several times telling me I was using an old Firefox profile. I tried to investigate, but each time your instructions told me to look for something as the last or next-to-last step, I ended not being able to find it on my computer. Again, I have tried everything. Please help me.