YOU SAID:

The cat sat at the mat with a bat

INTO JAPANESE

猫はバットでマットに座った

BACK INTO ENGLISH

Cat sat on mat with bat

INTO JAPANESE

猫はバットでマットに座っていた

BACK INTO ENGLISH

The cat was sitting on the mat with a bat

INTO JAPANESE

猫はバットでマットの上に座っていました

BACK INTO ENGLISH

The cat was sitting on the mat with a bat