You can connect the SU48R3XLBP to an SUA3000RMXL3U , by using the SUA039 extension cable as an adapter.
Connect one end of the SUA039 to the half of the connector with the 2 thicker wires coming from the battery pack as illustrated below.
Connect the other end of the SUA039 to the UPS. This will allow you to continue using your legacy battery pack with your new UPS. Please make sure to add the battery pack to the UPS interface via Powerchute Business Edition or a Network Management Card.