MacBook Pro iTunes music missing after data transfer

I bought a newer Macbook Pro and had the info on the older one transferred by a local shop who are Apple techs. Months later, I decided to play some iTunes while working - and none of the music will play. For any song I choose I get this message: "The song “Windham Hill 86” could not be used because the original file could not be found. Would you like to locate it?” If I say yes, then it sends me to another file which has nothing to do with my music collections.

While at the Apple shop (same guys) for an iPhone issue, I remembered to ask the question. I was advised to open Account/Account Access under iTunes and to remove any other names except mine. Everything looked good. Still no music.

Does anyone have any suggestions before I trot back to the Apple techs? Thanks for any suggestions !