Wondering about lodger duties elsewhere with 〜だろう

Grammar Explanation: Presuming with 〜だろう and 〜でしょう

Since Cocoa helps out at Chino’s house where she’s saying, she considers the situation if she were instead staying with Chiya.

ココア:: 「私(わたし)の下宿(げしゅく)先(さき)が千夜ちゃんの家(いえ)だったらここでお手伝(てつだ)いさせてもらったんだろうなー」; "If my lodging was at Chiya's house, I wonder if I'd be made to help out here."