There have been a number of times when I get panicky calls from Lightroom users because all their images are missing and/or have question marks on them meaning that Lightroom can’t find the original photo. My first question is always, “Did you move the pictures or folders while outside of Lightroom”? The answer is usually yes.
Do not move your images around using Explorer or Finder. If you do this, the Lightroom database will have no idea where those images are. Always move your images from within the Lightroom Folders panel inside the Library Module.
If you are moving your images from one hard drive to another (for instance, from an internal hard drive to an external hard drive), throw any photo onto the new hard drive using Explorer or Finder and then import that image into Lightroom. That will register the new hard drive and it will now show up inside the Folders panel. You can then create folders, move folders or individual images by clicking and dragging folders and images while inside the Folders panel. If you do it this way, Lightroom will keep track of where the original images are and you will be golden.