A return could only have occurred within the first 30 days from the invoice date. There is no way around that policy. You will need to purchase and install a 3rd party RAID expansion card that would fit into the motherboard PCI Express x1 card slot. Look locally for one like this.
I guess I don't see why this is becoming my problem when it is Dell that has not provided the equipment to perform as that they stated it would. It should be Dell's responsibility to resolve this issue and take responsibility for their error. Not make your error my problem. That is bad customer service and not standing behind your product.