Accessing files on external drive - Help please!

Greetings community.

I am hoping you can point me in the right direction with this one:

Using my external SSD drive with already >1TB data on it (family pictures and videos), I want to add it to my Nextcloud install, allowing me to access these files from Nextcloud.

Home server running OMV with Nextcloud installed as a docker through Portainer.

Steps taken so far:
Enabled “External storage” app in Nextcloud. I can now see (in admin settings->system) my external SSD and I can see that it is almost full (because of the already existing data on it). However I cannot see the actual files.

Additional Notes:
My level is a beginner level and I struggle mostly understanding what to type under “volume mapping” in Portainer when deploying or editing a docker install.

If you share your Docker Compose we can help you but…

The gist is you’re going to tell Docker to bind mount your external HDD volume into your Nextcloud container. This will make it available within the Nextcloud container.

The entry to add in your Compose will be something like the following (add to your NC container definition):

    - /path/to/external/drive/on/host:/mnt/extdata

Note that /mnt/extdata is arbitrary. It should be wherever you’d prefer the data appear in the container. Technically it doesn’t matter beyond personal preferences. It’s often something under /mnt or /media in small installations. (It won’t be the path in Nextcloud for day to day use so don’t stress too much about it).

At that point you can use the Local mount capability in NC’s External Storage app. Point it at /mnt/extdata or whatever you chose and set it to appear in NC with whatever folder name you’d prefer.