strapi/packages/strapi-generate-new/files/config/environments/development/database.json

{
  "defaultConnection": "default",
  "connections": {
    "default": {
      "connector": "strapi-mongoose",
      "settings": {
        "client": "mongo",
        "host": "localhost",
        "port": 27017,
        "database": "development",
        "username": "",
        "password": ""
      },
      "options": {}
    }
  }
}