Dockerized Nginx not forwarding to Dockerized Gunicorn

I am successfully running my Django web application using Gunicorn inside a docker container. This is running on a Ubuntu 16.04.6 system. What I am trying to do is have Nginx (running inside a Docker container) act as my web server and forward the http request to the gunicorn docker container. I have attached the relevant docker files. Note: At the command line I can execute my nginx image and have it successfully ping the gunicorn one by using: sudo docker container exec -ti 11e65460b93c ping django_web where 11e65460b93c is the container id of the nginx container and django_web is the name of the gunicorn container.

When I browse to http://my_ip:1337/ I get the message:
Welcome to nginx!
If you see this page, the nginx web server is successfully installed and working. Further configuration is required.

I don't know what that further configuration is.

Thanks,
Phil