YOU SAID:

There is a dog in the yard and I don't know who's it is.

INTO JAPANESE

庭に犬がいて、私はそれが誰なのかわかりません。

BACK INTO ENGLISH

I have a dog in the garden and I do not know who it is.

INTO JAPANESE

私は庭に犬がいて、それが誰なのか分からない。

BACK INTO ENGLISH

I have a dog in the garden and I do not know who it is.