What did Radical Republicans want from the Southern states before they
could rejoin the Union?

The radical republicans wanted the southern states to form an agreement to let slaves gain the right to vote.

the answer to fill in the blank in this question would be the word resource, it is defined as the money, material or people (since human resource is a very valuable good) that a company or a person has at disposition (meaning they can use the resource as they see fit), to be able to complete a task or achieve a goal.  

missouri compromise of 1820 which prohibited slavery