Where do I find my dbname for MongoDB connection string?

Who have try the precedent answers and it won't work like me, you just have to include the --password field with the URL you have to past it in your shell,without missing to change the dbname to the default dbname 'test' exmple: mongo "mongodb+srv://cluster0.otnlg.mongodb.net/test" --username mourad54 --password txt147

For those who wanna create db in with GUI

By default, the <dbname> is test but to create your own dbname, you need to change the <dbname> to the name of database you're interested to use. MongoDB Atlas will automatically create the db for you based on the name.
For example: Creating a db for Qlabs with username=Que and password=pin123

mongodb+srv://Que:[email protected]/Qlabs?retryWrites=true&w=majority

If you have made an atlas account and went through the tutorial then they may have made you make a mock cluster, by default it's name will be Cluster0. That's what your will be.