To be clear, once enslaved, the persons belonged to the slave owner not to any part of Africa. If you mean where did slaves come from, then this was predominantly West Africa, but not exclusively so. Where a powerful group could round up and capture Africans, they would be sold as slaves by traders.
Around 50% came from West Africa: Senegambia, today’s Senegal, Gambia, Guinea-Bissau and Mali but a sizeable proportion came from the so-called Gold Coast, what is now Ghana, and the Ivory Coast. Many slaves were taken from the Gambia River region, running from the Atlantic into Africa.