Why can I no longer download my pics as jpg files to my computer?

I am not running any external apps but found a video showing me how to convert those HEIC files to jpegs on the phone. Just received notice of the OS update, I have it set to auto update, but whatever, so that is happening now. After dinner plan to find the same guy's other video on how to stop my Iphone from suddenly using this weird format/file that is not usable, since the other one worked well for converting my pics back. I still don't understand why I could not find any info on it on icloud help at all since it is a new issue and I can't be alone in finding that it doesn't work for my purposes. But searching the internet seems to be working. Thank you