I would usually say bluetooth, as iphones don't have removable storage.
However in my experience iphones cannot send files via bluetooth 🙁
Unless someone who has an iphone can say otherwise you will need a middle man in a manner of speaking, a computer or online account (cloud) you can save your photos to then access from the lg phone, possibly via usb or wifi, to transfer the files.
Sorry I don't know an easier way -_-