YOU SAID:

my dad farted and it smelled so bad

INTO JAPANESE

父がオナラしたら、すごく臭かった

BACK INTO ENGLISH

When my father farted, it smelled so bad

INTO JAPANESE

父がオナラした時、すごく臭かった

BACK INTO ENGLISH

It smelled so bad when my father farted

INTO JAPANESE

父がオナラをしたとき、すごく臭いがした

BACK INTO ENGLISH

It smelled so bad when my father farted