5 each CDRs burned 2001 will not open
In 2001 we backed up certain folders from the HD of a PPC Mac G3 to five (unbranded) 800 meg discs using, most likely, the Toast application. Today when attempting to open the discs to retrieve some archived business related files, I get the following message depending on which iMac I'm using.
On an iMac 27" running Sierra 10.12.6 when I insert the disc the message reads: "The disk you inserted was not readable by this computer." Note, however, that Disk utility recognizes the iMac internal "CD style" drive.
On an iMac tangerine running OS 9 the message reads: "This disk is unreadable by this computer. Do you want to initialize the disk?" Name field shows: untitled, the Format field: ProDOS zero K (It shouldn't show zero K because the 800 meg disks should be full of data.)
Naturally I don't want to initialize because I'm hoping to access folders and documents from these discs.
Is there some resource I should have on the 27" iMac 10.12.6 and/or on the Tangerine iMac OS 9.2.2 to enable the discs to open?
Attached are screenshots of an actual disc (#1) plus screenshots from the iMac Sierra 10.12.6 (#2) (#3)and OS 9.2.2 (#4)
Any suggestions on how, if possible, I might retrieve the files on these discs will be greatly appreciated!
iMac 27″, macOS 10.12