YOU SAID:

going to the store for milk my father never returned

INTO JAPANESE

父は二度と戻ってこなかったミルクを飲むために店に行く

BACK INTO ENGLISH

My father went to the store to drink milk, which he never came back to.

INTO JAPANESE

父はミルクを飲みに店に行きましたが、二度と戻ってこなかった。

BACK INTO ENGLISH

My father went to the store for milk, but he never came back.

INTO JAPANESE

父は牛乳を飲みに店に行ったが、二度と戻ってこなかった。

BACK INTO ENGLISH

My father went to the store for milk, but he never came back.