This looks to relate to the WD backup app (at least from a quick web search, which turned up articles like the one below).
What I would suggest you try is to take one of the files (e.g. PLQNT0.jpg5dfccfd4 above) - make a copy of it (do not work on the original) and try renaming it to its normal 3 letter extension (PLQNT0.jpg in this example) and see if you can open that.
The _LAST files look to be simple indexing files or something like that, and aren’t the files themselves (as you can see by their size).
