SAP to read EAN/UPC Numbers

Our company would get in product without a EAN number from time to time and we would create a SAP number for those products. The ones that had a EAN number we would use those numbers. The previous system we used would be able to read both the EAN and SAP number. We are in the process of solely using SAP and being told we can only use one or the other. Is there a way for SAP to be able to read either (both) number? If not we will have to go through our entire inventory and make it one process which could take months.