You may be able to use swarm mode or k8s with your NAS as a master and other box as as a worker, but really theres very little point. As others have said, exporting volumes from your NAS via NFS and managing the worker using portainer or ssh to manage the worker directly might be better.

This kind of situation, where you have heterogeneous management systems with cross-cutting concerns is a great fit for Ansible - your playbook could provision the NFS volumes form the NAS and push the compose files to the worker at the same time, saving you from having to log in on both