Apple devices switched to using HEIC formatted photos from JPG back when iOS 11 was released.
Overall, the HEIC format is better than the JPG because it takes up less space but yet provides better quality. But it is only convenient so long as you stay within the Apple ecosystem.
If you also use Windows or Android devices, you’ll want to switch back to JPG format as the default for new photos.
This article will show you how to convert HEIC photos to JPG as well as how to permanently save your photos as JPG on your iPhone.