Orange,
I've never owned an A2000 - so what I'm about to say may be b*ll*x....
..... if the 3.5 floppy is an Amiga floppy and the A2000 supports two internal drives, then the drives should work as you've jumpered them.
But - afaik - the floppy cable doesn't have twist in it. If yours has the twist, then it's probably off an IBM based system.
Also, the A2000 may have an onboard jumper that enables support for the DF1: as an internal drive as opposed to having an external DF1: connected to the disk drive port.