Peplink 1350 simple port forwarding

I have a unit of pepwave 1350 that is connected with two WAN’s (WAN1 + WAN2),
we would like to create a simple port-forwarding so that if someone is trying to access the WAN1 ip address it will forward the traffic to internal ip.
for example
my WAN1 ip is 1.1.1.1 , WAN2 ip is 1.1.1.2
The traffic should arrive from 1.1.1.1:5000 to 192.168.1.1:5000

btw, we found that under ‘custom service forwarding setup’, we cant choose WAN ports.

Please advise.
Thanks