omv 5 - can't get nginx to run

I am completely lost.

Replacing Pi3B+ ( OMV4 ) with Pi4 ( OMV5 ), and found that I can't simply move the SD card from Pi3 to Pi4.

Followed TechnoDad videos to get a new image on to the SD and install OMV. OK to this point.

On the OMV4 / Pi3, I had nginx running as a plugin.

If I understand correctly now, with OMV5, these plugins ( which had system wide access ) should now be run in a self-containing bubble, Docker.

I guess Docker is the OS for these bubbles, and Portainer is the User Interface for the bubbles / dockers.

So using Portainer > App Templates, I found nginx and 'Deploy Container' ( I assume this is the equivalent of an install )

Next, went to Portainer > Containers and I see the "PiWeb' named container in the list.

I can browse ( on my PC on same network ) to the IP of the Pi4, and I get the " Welcome to nginx " screen.

On the Pi3, I had the web folder that nginx set as a shared folder, so that I can access it from my local PC as a network folder.

The nginx plugin listed the server root as : /dev-disk-by-label-NAShd1/www/

How / where do I change the settings in nginx / Portainer to use that same specific folder for the web pages ?

after a load of digging with Cloud Commander, I found the default index.html page here :

/var/lib/docker/volumes/c045ac8ef091973de611ad602b647cbfdf8e8181d470b9ee2d13f26e60cb6a46/_data

Verified by editing the file, changing a character, and saving. When viewed from my PC browser, the change is visible.

So having found the location of the files, I tried adding the path as a Shared Folder in OMV5, and added to SMB so I can map as a network drive from my win PC.

The network map connects, but I can't see any of the 3 files that are in the folder on the Pi.

Is this a setting, or better solution - how do I specify the folder for nginx to use, as a different shared folder ?