The narrators were separated from their birth parents
The first passage starts with the narrator's opinion of selling children. That gives us an idea of what the second paragraph is about. The sentence where it said the woman pretending to take me in her arms, indicates that the woman is not the narrator's mother but she acts like it. A child would not call his/her mother a woman.
The second passage is clearer with this fact. "and left me about half a year old, and in bad hands". This indicates that the narrator was left with someone besides his/her parents. The "her" the narrator mentions in this passage his/her mother, and when it states that she was transported to the plantation it is inferred that the narrator did not go with her, as it said he/she was left.
Hope this helps :D
Formal style, it's pretty easy to figure that out by just canceling out the other answers. Slang is obviously not it, I don't see anything critical in this, and I don't know how it could be informal.
The McKee's apartment. Hope this helped (hated that book)
