Have you given any thought to using thumb drives (usb sticks, pen drives...) ?
They hold a lot more pics, and are generally easier to use.
If the dvd is seen in "computer", have you double clicked on it there to attempt to open it .......that may show you what is already on the dvd........if you have a pic you wish to transfer to the dvd then you would right click on the pic and select 'move to'...or 'copy to' ...dvd (the dvd may have a different name to identify it../? )
Sorry if I appear to be grasping at straws here......but I am !....I dont have a working dvd draw on this tower to experiment with.....so I am having difficulty giving precise instruction !
The reason I ask about the desktop environment is because with both my Linux and Mac computers that is all that I use to burn files to a disk. But I don't think that you are using the same file browser as me. I think the Cinnamon desktop environment is standard for Mint. Cinnamon uses Nemo for its file browser. I'm sure it would have the same functionality as any other Linux file browser.
In both my Mac and Linux computers a burn button shows up in the top left corner of the file window after I click on the disk icon in the file window.
When you have a disk inserted in the drive and you right click on a file that you want to burn is there a 'Burn to disk' option?