How do I restore my iTunes playlist

I successfully imported new songs onto my iTunes last night. This morning, I noticed that nearly 75% of my files were not listed on iTunes and that ALL of my playlists were gone as well.

How do I restore my iTunes back to how it was yesterday? I want all of my playlists and imported songs and albums with the cover artwork that I uploaded. I was able to successfully add all of my files onto iTunes, but they are all back to being unorganized.

PLEASE HELP!