We plan to add a convertor to iExplorer for HEIC files for those who would rather have a more compatible format such as JPEG. For now, there are many free convertor apps you can use on both Windows and Mac as well as several free website apps. Here is a link to one of the web apps to convert HEIC to JPEG:
Then, in iOS, for saving future photos in a format other than HEIC, you can change your camera settings to save in JPEG instead. Just tap Settings > Camera > Formats > select Most Compatible (JPEG/H.264).