IPhones' default photo format is HEIC, something that Windows doesn't open by default.

Not sure if it works for HEIC, but here's a tip for converting WEBP (common on websites) to a more universal format like PNG:
1: open Paint
2: open .WEBP in paint
3: save as -> PNG
4: give name and save

There's also a Firefox extension that I use that that lets you just save as PNG https://addons.mozilla.org/en-US/firefox/addon/save-webp-as-png-or-jpeg/