Just drag and drop them in the Lightroom folder panel. If the new drive does not show yet in the folder panel, then click on the plus icon in the upper right corner of the panel and choose to create a new folder (that you then create on that new drive). If you drag and drop in Lightroom, then the folders remain linked.
Alternatively you can copy the folders to the new drive in Windows Explorer / Macintosh Finder. Then in Lightroom, right-click on the top folder of the copied hierarchy and choose 'Update Folder Location'. In the dialog that follows you can navigate to the new drive and select the corresponding folder. The folder and all its subfolders will now show on the new drive, and no longer on the old drive. Once you have relinked the folders in Lightroom, you can delete them from the old drive too.