Firewall NIC need a subnet mask.

I would like to install a firewall for our network. The firewall requires two NIC with a different subnet mask. Our ISP gave us this static address 221.229.043.012 (sample only) and the server NIC they placed was 139.179.118.118 (sample only). Our local network address is 139.179.244.000 to 255. What subnetting should I do here for the second NIC of our server?