A database dump is the correct answer as it typically includes the complete data set as well as the database structure, which can be crucial when migrating to a different system. While backups and exports are also used for moving data, they often serve a different purpose or might be more system-specific. A flat file export, while it may seem like an appropriate choice, might not effectively maintain relational data integrity or the original database constraints when imported into a system with a different structure, thus making it a less optimal choice for complex migrations.