Why did Reconstruction include the Thirteenth, Fourteenth, and Fifteenth Amendments?

I'm stuck on this question. Sites for help or hints/help to get the answer would me much appreciated!

2 answers

https://www.senate.gov/artandhistory/history/common/generic/CivilWarAmendments.htm

What do you think?
My computer glitched and I didn't see your answer before =(

So, all of those amendments have to do with resolving slavery and taking away free and slave states, so the entirety of USA is free?

P.S. Thank you so much for the help!