The source and destination disks are not the same type. Make sure the disks you choose are the same type, and then try again.
The formats of the disks you want to copy with the Diskcopy command must be identical. The disks you have specified have different formats. For example, one floppy disk may be a 5.25-inch disk and the other may be a 3.5-inch disk.
Retry the Diskcopy command, using floppy disks with the same format.