1. To create a Union that could be perfect.
2. To be a more righteous nation.
3. To help the nation to be more secure and bring peace.
4. To give provision for the common defense
5. To spread the idea of having general welfare.
6. To generate a nation that secures all the blessings and increase the prosperity for ourselves.
Step-by-step explanation:
Still, a bit confused about this question but I think this is what you were looking for; the reasons the preamble was written.