The server value of the Power BI dataset is visible in the status bar (bottom-right corner) when connected to the dataset from DAX Studio, as shown in the following screenshot:
In the following code, the server parameter is localhost:52809. To obtain the database parameter, run the following query in DAX Studio:
SELECT [CATALOG_NAME] , [DATABASE_ID] FROM $SYSTEM.DBSCHEMA_CATALOGS
Both columns will retrieve the same GUID value that can be used as the database parameter.