At Ease 3.0 and At Ease 3.0 for WorkGroups are available only on high density floppy disks. The outside of the box explains that the media is on 1.4 Mb floppy disks and an Apple SuperDrive floppy disk drive is required.
If your 800K drive equipped Macintosh computer is on a network, you can install At Ease 3.0 by doing a network install. The At Ease 3.0 for WorkGroups Administrator's Guide explains how to do this starting on page 20. You can also refer to the TIL article "Software Installation Over a Network" for a description of how to do this procedure.