Does /dev/sr0 exist?
If so, try running
sudo mount -o ro,unhide /mnt/sd0 /mnt
then find all the files in /mnt.
When you are done using it, run:
sudo umount /mnt
Usually, there is an entry in the /etc/fstab to automatically mount optical drives to /cdrom. Alas, none of my systems have that line, so I can’t just copy it here for you to add. It is dependent on the device name. That the name that the kernel creates when it finds the optical hardware during boot. /dev/cdrom0, /dev/dvd0, /dev/sr-something are all commonly seen.
Hummm. thinking a little more, most of my systems don’t have a DVD connected, which explains why there aren’t any devices. On the 1, older system with an optical drive, I see these files in /dev/:
sr0 cdrom cdrw dvd dvdrw
Any of those could be used as the mount device.
BTW, this might not be obvious, but a data disc needs to be inside the drive and it needs to be closed to mount.