Try looking at a VM in the cloud such as Google Cloud Platform or Amazon Web Services. I prefer GCP over AWS, but there are many other options. You just need a ubuntu or debian OS to Install Plone.
I think you may be looking for something like SQL tables. Senaite is built on Plone, which uses ZODB, an object database. Read the Plone docs.
Data stored in docker doesn’t exist when the container ceases to exist. There are ways to make this work, but you would need to delve deeper into the Docker docs. If you are setting up a production instance, I don’t recommend using docker. Instead, run your Plone instance in zeocluster mode to achieve the same outcome as a Docker Swarm.
This is covered in multiple locations but if in doubt, google it.