YOU SAID:

i went to the store to grab some milk for my father who has cancer

INTO JAPANESE

私は癌の父のために牛乳を買いに店に行きました

BACK INTO ENGLISH

I went to the store to buy milk for my father who has cancer.

INTO JAPANESE

私は癌を患っている父のために牛乳を買いに店に行きました。

BACK INTO ENGLISH

I went to the store to buy milk for my father, who has cancer.

INTO JAPANESE

私は癌を患っている父のために牛乳を買いに店に行きました。

BACK INTO ENGLISH

I went to the store to buy milk for my father, who has cancer.