Momof3

I have recently moved all my images to an external hard drive to have my MAC cleaned out. I'm trying to now work on my last few sessions and when I go into LR, its showing "File Not Found" and the catalog date is no longer bright white as it is when I import from my SD card directly normally. My question is: How can i get my images back to being able to edit them via LR? (I can see my images in LR via catalog in library, but) I appreciate any help and I'm just crying over here :-(Help