YOU SAID:

i would like to have 20 cats

INTO JAPANESE

私は 20 の猫を持っていると思います

BACK INTO ENGLISH

I think I have 20 cats

INTO JAPANESE

私は20匹の猫がいると思う

BACK INTO ENGLISH

I think there are twenty cats

INTO JAPANESE

私は20匹の猫がいると思う

BACK INTO ENGLISH

I think there are twenty cats