Where do I send Mastercard credit card payments? The mailing address is: P.O. Box 2711, Omaha, NE 68103-2711 Additionally, following the conversion, you will be able to make your payment through a transfer in Online Account Access or at any 3Rivers branch. Have more questions? Submit a request 0 Comments Article is closed for comments. Related articles How do I pay a 3Rivers loan/credit card/mortgage/line of credit?