There are multiple ways to accomplish what you want to do. Could you provide any more information about how you are running Nginx with Docker? Are you building an image from your own Dockerfile?

Often you would copy the configuration files into the image while building it. Another approach is to bind mount a directory on the host system into the container. Assuming you are using the official Nginx Docker image directly, you could do something like:

docker run --name your-nginx-container -v /local/path/to/nginx.conf.d:/etc/nginx/conf.d:ro -p 80:8080 -d nginx

Where /local/path/to/nginx.conf.d is a directory in the host filesystem. You can then drop additional Nginx configuration files into that directory and they will be used inside of the container. For Nginx to pick up the new configuration, you’ll need to restart the process with:

docker restart your-nginx-container