Disklavier

I have a upright yamaha piano with a disklavier MX-100A.  I purchased a 
box of new 720 disks.  When I place the floppy disk into the unit it 
gives a "Convert Disk" message in the display.  I have scoured the 
handbook and there is no command to format the disk on this unit (or is 
there?).  Does anyone know how to overcome this problem?  Thank you.