This is the 1387th most frequent Russian word.
белорусских
The word "белорусских" is a form of the adjective "белорусский," which means "Belarusian" or "of Belarus" in English.
Here, 'белорусских' is used as an adjective modifying the noun 'книг', describing the origin or association to Belarus of the books.
Он прочитал множество белорусских книг.
He has read many Belarusian books.
In this sentence, 'белорусских' functions as an adjective describing 'городов', indicating that the cities are located in Belarus.
Мы посетили несколько белорусских городов.
We visited several Belarusian cities.
Here, 'белорусских' modifies 'блюд', representing the characteristic of the dishes as belonging to Belarusian cuisine.