The screenshots provided were of different locations.
Gallery shows Camera while the PC shows SD Card > DCIM
The folder SD Card > DCIM > Camera is the right files that you should be checking/showing on the screenshots to co-relate with the Gallery screenshot.
The Gallery screenshot may not display the image/thumbnail if that file was encrypted, by the android system or an app, it shows that blank image/thumbnail because the file is still on a JPEG (or other like PNG/GIF) container but the contents were not since it was encrypted.
The PC screenshot will co-relate to the Gallery if you select Album on the drop-down at the top where it says Camera and since you tried viewing it on the PC, chances are those were encrypted as well.
Your files may still show that it is .JPEG/.JPG (unlike some encryption that uses a different file type, like .MUDP) which are containers only and most photo/picture programs will indeed recognize it but the contents inside the container were unreadable due to a possible encryption which jumbles it.
Worst case scenario, if you never applied encryption or something encrypted it, is corrupted files.