Translation:There are three automobiles on the street.
In an earlier lesson, 'per strada' was used when talking about 'uomini'. Is there a slight difference in meaning between ''nella strada' and 'per strada'?
I would rather say "per strada" or "in strada" than "nella strada". But there is a slight difference.
"per strada" and "in strada" are generic.
"nella strada" could be a specific street, maybe the one you can see, or the one you were speaking about in the sentence before.