Revert back to NEF file

I am planning to enter the Wildlife Photographer Of The Year Competition in October this year. My concern is that if I get short listed ( maybe wishful thinking ...) I would need to provide a copy of the original NEF RAW file. As I understand it; Lightroom converts my images to DNG files, from which I do the processing. So any advice on how to go back to the NEF file would be welcome. I clear my XQD and SD cards shortly after uploading, so can't go back to them. I use a Nikon D850 with Lightroom CC on an iMac.