where is info in the itunes description field stored

We recently purchased a Mac Mini with enough storage to hold all of my music and photo files. I successfully transferred both sets of files from an external hard drive to the SSD of the Mini, but somewhere along the way the data that I had entered in the description field of about 4500 iTunes songs disappeared. My suspicion is that one or another of the iTunes support files didn’t get brought over, but I don’t know in which file this data is stored. I populated the field with dates for when the songs first showed up on the Billboard Top 100 so that a playlist would play in approximately the order that the songs actually achieved fame. It worked well when I had visibility to the dates but I’m hoping I can recover this info and not have to go through the effort to populate the field again.