Traffic route

Hi Guys,

I need your help.

I have a windows server and router connected to fortigate 100d. for our outside interface WAN1 , Internal Interface - server

The router is from our client,  it is connected to other port of firtigate. 

the scenario, how can i configure the traffic route, that if i will do the tracert command, it should be like this

--- > subnet from the server

--- > interface IP of the firewall

----> IP of the router from the client

----> IP of the WAN 1

but, i did it in the policy configure the outbound policy, it doesn't work.

Please i need your help.

Thank you.