How do you bring back the oringial Fallout4_en.STRINGS, Fallout4_en.DLSTRINGS, and Fallout4_en.ILSTRINGS files?

I would think you could 'verify integrity of game cache' in order to do this.

If this has anything to do with Full Dialogue Interface, it comes with a folder containing backups or the originals.

But yes, verify integrity will replace any missing files (delete your modded ones so it notices their absence).