YOU SAID:

there's a cow in my house

INTO JAPANESE

私の家には牛がいます

BACK INTO ENGLISH

I have a cow in my house

INTO JAPANESE

家に牛がいます

BACK INTO ENGLISH

There is a cow in the house

INTO JAPANESE

家に牛がいる

BACK INTO ENGLISH

There are cows in the house

INTO JAPANESE

家には牛がいます

BACK INTO ENGLISH

There are cows in the house