This is the 13431st most frequent Polish word.
papierosów
"Papierosów" means "of cigarettes" (genitive plural form of "papieros").
Here, "papierosów" is the genitive plural form of "papieros" and is used to indicate the content of the pack.
Mam paczkę papierosów.
I have a pack of cigarettes.
In this case, "papierosów" is again in the genitive plural form, used as the object of the negation verb "palić."
Nie powinno się palić papierosów.
One should not smoke cigarettes.
Here, "papierosów" is in its genitive plural form, used to specify the quantity indicated by "kilka."