Backup of originals to SSD?

I’d like to back up to an SSD my original nef files that I have imported from an SD card into CO on my iPad. I have tried copying the original images from within the CO directory on the iPad but find that this replaces the photo’s date and time with the time the photo was imported to CO.

Does anyone have advice as to how I can do this? I only carry an iPad and SSD on my travels and don’t have enough memory to keep duplicate originals on the iPad.