I'm not clear on what you're trying to do, exactly.
If you have imported images from one drive, and have the exact images (with folder structure) on another drive, you just need to right click on the top-most folder in the Folder panel. Choose "Update Folder Location" and navigate to the new drive. This will point Lightroom to the files on the second drive, but not touch the images on your original drive.
If you want to keep the images from the original drive, AND have Lightroom work with the images on a second drive, just import the images from the second drive. The drives will appear separately in the Folders panel, making it easy to move between the drives.
If I am not understanding your question, please give more specifics.