It’s not definitive and I’m sure both figures are low estimates. I know that the state kills and enslaved far more, but a quick Google search yields these screenshots. 
Discussion
"New World" is the entire western hemisphere, so not representative. The closest I found was a little under 4 million in 1860. https://www.worldatlas.com/articles/slave-population-of-the-early-united-states.html
Horrific on all sides. Humanity still strives to be free
Yea, this is why I said these numbers are all lowballs, because if there were just under 4 million in 1860, how many were there total from beginning to end? That number is much bigger and same goes for the white slaves the Barbary pirates had. The Arab slave trade of several “races” was much bigger than the transatlantic too, nobody talks about that lol I live in the USA so I focus on it for that reason.
Once the modern state came about it dwarfed those slavery numbers. The modern state is much more efficient at running massive slavery operations.
I’m not going to lie, every time I hear talk of reparations I immediately imagine how much btc I could buy with it 😂
History is a story written in blood; the things mankind has done to itself can be quite shocking. The only way towards a peaceful, prosperous future is not an eye for an eye but forgiveness. "Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you." Ephesians 4:32