Transferring non-purchased iTunes library

I recently purchased a Macbook air to replace my VERY old Macbook Pro. ALL of my music is on the MB Pro - Both purchased and my entire CD collection that I ripped into the computer. I have tried several ways to transfer the files, but only the purchased songs are transferring. I am now able to successfully "see" my whole music library, but when I go to play a non-purchased song (one of the ones from a CD that I previously owned and added to the computer manually), I get the following message: The song “It's the Most Wonderful Time of the Year” could not be used because the original file could not be found. Would you like to locate it?

When I say yes to locate it, it takes me to my Finder home page. What am I doing wrong? How can I fix this? I am super frustrated and the Apple store is closed indefinitely!