Your folders in Lightroom should still appear on the C: drive, with a question mark icon. You need to re-connect the photos inside of Lightroom by following these instructions: Adobe Lightroom - Find moved or missing files and folders
I should have said, I made a copy (with a new name) of the image folder from the C: drive to my D: drive. The D: drive is not even showing up as an option in LR for me to think about finding and re-connecting the new folders.
I hope this is making sense. I'm not sure how else to express it
Making a copy doesn't change anything. Lightroom still doesn't know about your D: drive because you made the copies in Windows. As I said, you must connect the D: drive photos to Lightroom, following the insturctions at the link I gave you (scroll down to the section entitled Updating Folder Location)