MongoDB 3.0 introduced major changes to the MongoDB tools in order to support additional storage engines such as WiredTiger. In MongoDB 3.0, mongodump and mongorestore do not support the --dbpath option. As such, you cannot use this procedure for a partial data restore on a mongod running MongoDB 3.0.
If you anticipate you will want to restore a single database, create a backup for just that database by excluding the databases or collections that you do not want to back up using the Blacklist field in the Advanced Settings.