One NGINX load balancer for two functionnalities

Hello,
I'm looking for some help on NGINX as a load balancer.

I currently have the attached configuration file which represents production instances. NGINX redirects everything that happens on ports 80 and 443 to my production instances to production.

I would like to add two test instances such as:
www.monserveur.fr:8080 (http) --> www.monserveur.fr:8181 (https)
www.monserveur.fr:8181 (https) --> www.monserveur.fr:31081 or www.monserveur.fr:32081

how can I set this up in NGINX? do I need to create other server sections {} and another upstream session {}

I need your help to move forward.
thanks
thierry