This is the 13262nd most frequent Russian word.
молочной
"Dairy" or "milky."
In this sentence, "молочной" is an adjective modifying "шоколадку," indicating that the chocolate bar contains milk or is related to milk.
Она купила молочную шоколадку.
She bought a milk chocolate bar.
Here, "молочная" is an adjective related to "промышленность," meaning it pertains to milk production or the dairy sector.
Молочная промышленность в регионе развивается.
The dairy industry in the region is developing.
"Молочной" functions as an adjective describing "фермы," specifying the type of farm, which is related to milk production.