When you want to tell someone which apartment or room you live in, you can use this expression. 

It is commonly used when introducing yourself to neighbors, delivery workers, or the building staff to clearly explain your apartment or room number.  

English: I live in apartment/room 101.

Korean: 저는 101호에 살아요. 

Korean Romanization: Jeoneun 101hoe sarayo.(Jeo-neun baek-il-ho-e sal-a-yo.)