Hello There! ^_^
Your question: What were the three parts to the Union's plan to defeat the South in the Civil War..?
Your answer: The three main parts were:
1) Blockade all the Eastern and and Southern ports in the Confederate States.
2) Control the Tennessee valley and march through Georgia to the coast.
3) Divide the South by taking control of the Mississippi River.
Thus, this plan was called the 'Anaconda Plan'
Hope this helps!