How do I upload old photos from my iPhone to my PC?

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When I plug my iPhone into the PC it uploaded any pictures that were recognized as new. There are other photos on my phone that I'd also like to upload/back up that I cannot locate in the DCIM folder or anywhere else. I can see them in my iCloud Photo Library but if I delete them from my phone those will be lost without an actual back up. Any suggestions? Thanks in advance.