Acrobat Reader doesn't open your pictures, and can't convert anything. But Windows or Mac OS is confused. Just start your NORMAL picture viewer, and open the files. What is your normal picture viewer?
Sorry for the delayed response and inconvenience caused. It seems that the file association is broken and as Aandi correctly mentioned that Adobe Reader does not open pictures and cannot convert anything.
Please change the file association once, refer to the steps mentioned in the following Adobe article: File associations broken | Windows
assuming you are using Windows machine, right click on any Picture>Select Open With>Choose another app>Choose the picture app>Select the checkbox 'Always use this app'.
let us know how it goes and share your observation.