Realisticly speaking, if you already have the HDD's I'd have no idea, there are 2.5 to 3.5 bay adapters but they can be very case dependent and I'm not 100% sure you could pull them off in that case. If you don't have all 4 HDD's yet, you could get 2 3.5mm HDD's and 2 2.5mm HDD's. If you can...