Brian,
on the new 5''GB drive, create a folder with just one image in it. Catalog that image. You can discard this image now that Lightroom is aware of the folder on the drive.
Now, with one or more of the other drives connected, drag the folder(s) relevant to that drive within LR into the new folder on the 5''GB drive.
You can only move one folder at a time but you do not have to wait for the folders to finish moving before selecting the next one.
IE. Click Drag Click Drag Click Drag Click Drag - in rapid succession will work.
The result, is that LR now knows where the images live on the new drive because IT moved them.
The time taken literally depends on the speed of your system copying (moving) files from one drive to another.
An alternative method:
If you have all the drives attached at the same time then select All Photographs and make sure all thumbnails are actually selected. From the File menu select Export as catalog.
Then make sure you check the box that enables Export negative files.
Save this catalog onto the new drive. All the images are COPIED as opposed to moved along with the new catalog.