This is the 4406th most frequent Russian word.
вечерних
"Evening" (adjective, relating to evening).
The word "вечерним" acts here as a descriptive adjective modifying "улицам" to denote the time of the activity.
Я люблю прогулки по вечерним улицам.
I like walks on evening streets.
The word "вечерних" functions as an adjective modifying "нарядов," specifying the type of dresses designed for evening use.
Мы посетили выставку вечерних нарядов.
We visited an exhibition of evening dresses.
The word "вечерних" modifies "мероприятий" to highlight the time period during which the events will take place.