The ACA 500 is an Amiga 500 expansion and I thought the Minimig doesn't have a floppy port.
Are you trying to get this working on a Minimig (in which case just use the Minimig's emulation to do both) or on an A500 (in which case just connect both, as they use different ports).
Sorry, maybe I'm being thick (quite common this time of the morning

) but it's not clear what you're trying to do: expand an Amiga or use a Minimig.