According to the preamble, what are the purposes of the cconstitution?

As the preamble says, "We the People, in order to Form a More Perfect Union, Establish Justice, and insure Domestic Tranquility, Provide for the common defense, promote the general welfare, and secure the blessings of liberty."

The purposes of the Constitution, then, are to:
Make a more effective country than the Articles of Confederation did;
Make sure that there is a fair and equal legal system;
Keep the country stable;
Protect the country and its citizens;
Ensure that all those citizens can live reasonably happy lives;
And Create a system where all people are free and equal.