Neither the Apple ii 5.25 nor the old Mac 3.5 drives are compatible with IBM. The files can be transfered either via serial port with comm programs at each end, or by using an Apple //e or //c or IIGS with both 5.25 and 3.5 drives. I f the Mac's not too old it will be able to read ProDOS formatted disks. Best bet is to use a IIGS with GSOS System 6 which can write to Mac formatted disks.