If you really want to be safe use a file-synchronization utility like FreeFileSync:
http://sourceforge.net/projects/freefilesync/
It also transfers file faster than using Windows Explorer. Synchronize the top-most level folder between the two drives using Freefilesync's 'Mirror' copy mode. Once completed I would also check the file count and 'size on disk' using Windows Explorer. They should be the same. Then do 'Update Folder Location' from inside LR.
Make sure you have a second copy synchronized the same way on a 2nd backup drive. Also disconnect your original drive and put it in a safe place. In the unlikely event the new drives (primary & backup) suffer data loss you can at least recover all images from the original transfer. Early drive failure in the first 1,000 hours is not uncommon, so use a SMART utility to track drive health.