YOU SAID:

My friend's cat had 6 kittens.

INTO JAPANESE

友達の猫は6匹の子猫を飼っていました。

BACK INTO ENGLISH

My friend's cat had six kittens.

INTO JAPANESE

友達の猫は子猫を6匹飼っていました。

BACK INTO ENGLISH

My friend's cat had six kittens.