Copying photos from iPad to PC

Hi Folks, I am using an iPad Air 2 that has been was my daughters and my wife's before her. It is running low on storage, so I want to transfer a lot of the photos to my PC. When I connect my iPad to my PC , via USB, not all of the photos are in File Explorer. I can see the DCIM folder and 4 sub folders (100APPLE, 104CLOUD, 105Cloud and 106Cloud but there are photos on my iPad that are not in any of these folders. Any ideas what I need to do?

Thanks,

Trev