YOU SAID:

My cat ate the the baby duck i found on the grass

INTO JAPANESE

私の猫は草の上で見つけた赤ちゃんアヒルを食べていた

BACK INTO ENGLISH

My cat was eating a baby duck found on the grass.

INTO JAPANESE

私の猫は草の上で見つかった赤ちゃんのアヒルを食べていました。

BACK INTO ENGLISH

My cat was eating a baby duck found on the grass.