If you used the exact command I posted the folder would be accessible by browsing your “docker” shared folder on the NAS and then in the subfolder “zwavejs2mqtt”. The folder is mounted by this part of the command:
-v /volume1/docker/zwavejs2mqtt:/usr/src/app/store
The bold part is the folder used on the NAS itself, the other part is the path within the container. If you for some reason used a directory not in a shared folder then you’d have to SSH into the NAS to get to it.
PS: It might be useful to start a new topic in case you’d still need help.