How to move the domain server?

I just moved my domain server from old office to a new office. We are using a different ISP for the DSL. They have assigned us with a static IP address, gateway and DNS. We have a router connected with ISP modem and Netgear switch connected with the router. Router is set to DHCP and all the workstations are connected with the switch.

Question: We have dynamic ip addresses coming out from the router. How can i hook up the domain server(requires static ip address) with this switch and act as a domain? What changes do i need to make to the server?

You input would be really appreciated. Thank you in advance.