What groups would have to vote approval in order for this to be done if it were proposed to join Alabama and Mississippi to form one state?

Congress and the legislatures of both states, legislatures of both states and Congress, Congress and legislatures of both states, Congress and the legislatures of Alabama and Mississippi, Congress and the legislatures of Mississippi and Alabama , Congress and legislatures of Alabama and Mississippi, Congress and legislatures of Mississippi and Alabama , legislatures of Mississippi and Alabama and congress, legislatures of Alabama and Mississippi and congress, the legislatures of both states and Congress, the legislatures of Mississippi and Alabama and congress, the legislatures of Alabama and Mississippi and congress, Congress, legislatures of both states, Congress, legislatures of Alabama and Mississippi, Congress, legislatures of Mississippi and Alabama, Congress, legislature of Mississippi, legislature of Alabama, Congress, Mississippi legislature, Alabama legislature, Alabama legislature, Mississippi legislature, Congress, Mississippi legislature, Alabama legislature, Congress, Congress, Alabama legislature, Mississippi legislature