Creating a DMZ setup

I have a simple consumer grade ADSL router that has a DMZ configured to a local ip of 192.168.1.1 . At this address sits the WAN interface of an OPNsense box. This is configured as an end point for VPN tunnels with traffic being passed to servers on the LAN. Outbound traffic from the LAN is unrestricted and is required for fetching updates, some browsing etc.

I want to replace the aforementioned ADSL router with an SRX320. How do I re-create the above i.e. create a DMZ-like setup that allows traffic to flow in and out as described above?