"여자아이가 개를 길에서 도와요."
Translation:The girl helps a dog in the street.
From my research both ("in the street" and "on the street") is correct when refering to a location on top of the road. Some native speakers use "in" and some use "on" depending on their region.
Some even use both. For example "on the street" when they talk about being either on the road or next to the road and "in the street" when they talk about experiencing the traffic.
However "living on the street" can also mean that you are homeless and "living in the street" can also mean that you are literally surrounded by asphalt cement. Context might matter. ;)
On the street does not have the same connotation as in the street. On the street is vague, could be in the middle of the road or on the sidewalk, but in the street means in the middle of the road or in the way (of cars). And because its 에서, i think "in" is more appropriate than "on"