If you installed on Docker, then the database runs in a container which is accessible only to the container running the CMS. If you have MySQL installed on your host machine, then by default the database won’t be in that MySQL instance. It’ll be in the one the CMS brings with it.
The database name will be “cms”, and the database username will be “cms” too, and the password will be the one you specified in config.env file.
You can connect to the database by following the instructions in the FAQ:
Keep in mind however that all interactions with the CMS should be either via the API, or via the web interface. We can’t offer you support if you’re making direct modifications to the database itself I’m afraid.