Restore the photos from your backups to their original locations on a new external HD.
Or restore the phtoos from your backups to some other location and reconnect in Lightroom via Adobe Lightroom - Find moved or missing files and folders
Thank you dj_paige but I only had files on the external hard drive....no other copies of files/folders anywhere. I can look at photo's in LR but can not download because 'no files are found'. Surely there's a way to download photo's from LR to a new folder.....somehow.....??
Well, no backups, the technical term for that is "a problem". I think from this point forward, you need to commit yourself to making regular automated backups of all of your photos and catalog file to different physical disks, no excuses.
Your photos are not stored in Lightroom. However, Lightroom does create "previews", this is what you are seeing, but these are usually smaller and low-quality compared to the originals. There are plug-ins that can extract the previews from Lightroom. One such plug-in is here robcole.com - PreviewExporter