Where do I find my Lightroom 4 photo catalog and how do I import it back into Lightroom after the data migration from an old iMac (Lion) to a new 5k iMac (Yosemite) failed to do it? When I open Lightroom on the new iMac it shows it is as being empty whereas before the data migration it had tens of thousands of images in it. All of my photos have always been kept on an external backup (Drobo 5D) and it seems that the link allowing LR to "see" all of the photo folders on my Drobo has been lost or is not recognizing them on the new computer. Any help would be appreciated. Thanks!