Before using MySQL or MongoDB to store your worlds, you've got to configure them. To do so, navigate to the SWM config folder located inside your plugins directory, and open the 'sources.yml' file. Inside there are all the parameters you need to set. Here's an example of how your sources.yml should look like:
file:
# The path to the directory where slime worlds are stored
path: slime_worlds
mysql:
enabled: true
host: 127.0.0.1
port: 3306
username: my_mysql_username
password: my_mysql_password
database: slimeworldmanager
mongodb:
enabled: true
host: 127.0.0.1
port: 27017
username: my_mongo_username
password: my_mongo_password
auth: admin
database: slimeworldmanager
collection: worlds
Remember to enable MySQL and/or MongoDB if you are going to use them!