if by “original images”, you’re talking about the true source images saved on your machine, as opposed to the “original” images downloaded from iNat to your machine, i don’t think there’s an efficient way to do this. (although iNat does provide the original filename on photo pages, i don’t think there’s an easy way to get this information short of scraping, and even then, filenames change. you could do some sort of image matching, but that would involve downloading a bunch of images.)
there are already existing repos in GitHub that offer various kinds of code to download data and images from iNat, but i would be hesitant to use them except in extreme situations because:
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you may be interested in: https://forum.inaturalist.org/t/naturtag-organize-your-photo-collection-with-inat-metadata/33959.