I am not sure that "belonged" is the right word. Perhaps "came from" would be better, but either way, you need to look at the central dream sequence that the slave experiences during his death-slumber. The one detail that definitely links it to Africa is reference to the river Niger, which is mentioned twice, first as he overlooks the scene which includes "the lordly Niger" and secondly as he rides his horse along the banks of the Niger. In addition, reference to the "bright flamingoes," the "tamarind," and other such animals as the lion and the hyena all clearly link the slave's dream to his home country back in Africa. Examining such details clearly indicates that this is a very strong and powerful dream of the liberty that the slave formerly enjoyed, which of course only serves to highlight the horror of his present state, being taken so far away from his home and forced to work under terrible conditions.
there are many points for this
1) slave's were of african origan mostly at dt time
3)dark eyed queen
4)flamingoes (not found evry where so a connection cn be made to africa)
7)desert ocean together..
i think he belongs to africa only particularly because at that point of time it was only from africa that the slaves were brought and also the mentioning of the river niger. also when he remembers his family he calls his queen as dark eyed which is a clear indication of african ,africans have a dark skin.