They are Israelites. Because if you look up the slave logs, they were the main ones being sold to the Americas & Carribean out of what now known as Nigeria.So they fit the prophecies. And alot of them had straight up Hebrew surnames, or Hebrew derived surnames. Some of them retained their heritage and customs as well and still claim to be Jews to this day...although the majority would go on to convert to Christianity and Islam.
But there's no way a DNA test can tell you this, because there's no way to truly identify what the genetic marker is of the Ancient Jews.