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I strongly recommend hard-assigning a fixed drive letter for your Seagate that is much further through the alphabet. That's because LR's paths depend on this drive never coming into competition, for a soft-assigned drive letter, with some other device which may already be connected too, on a given occasion.
If you assign (say) M, then that's well out of the way of something else accidentally grabbing D, or E, etc. This will temporarily 'orphan' all of your photos (which is fine).
Once you've done this, you can suitably re-browse the common parent folder of all the images that LR is currently showing within D - to the corresponding folder within (say) M. Then do the same thing for the images that LR is currently showing within E.
If that common parent folder is not showing, right-click on one of the top level folders that are showing, and select "show parent folder".
IMPORTANT: do not even consider re-importing anything. You only need to update the addressing (path info) for the images that are already imported, complete with all edits and organisation as they stand.
What happens if you re-path just one image that is marked as missing? (click on the [!] icon and choose Locate)