Welcome KD
I have no idea, sorry. I'm not sure where the bedroom in the back would be either. Maybe he meant upstairs in the back?
I just know the layout of the bottom seems to be lounge room at the front which moves into the dinning room which then moves into the kitchen. I presume the stairs to go down into the basement are in there & there's also a back door. Maybe there is a bedroom if you go under the stairs (going up) at the back of the house on that side of the house since everything that we see seems to be all on the left
Hopefully someone can help you out. That's pretty cool that you're trying to recreate it in your Sims game. I hope you can create it & find your answers!