The image is a picture snapped with an iPhone and uploaded from the photo gallery. As Criktor suggested, I am pretty sure the format was a .jpg
Unless you have a very old version of iOS, iPhone photos these days default to an HEIC format. There is a way to change it under settings/camera/formats, but if it is the default settings, you would need to copy the image out of photos to "Files", or send them to a computer, and can then get it into JPG.
As far as I know, the HEIC is the native picture file standard for iPhone, or maybe iOS, but as soon as an image is shared elsewhere, via WhatsApp, mail or exported through a browser extension, as I did, those are converted on the fly to either .jpg or .png files.
