YOU SAID:

I went to the store and I bought a jar of milk.

INTO JAPANESE

私は店に行って牛乳の瓶を買いました。

BACK INTO ENGLISH

I went to the store and bought a bottle of milk.

INTO JAPANESE

私は店に行って牛乳を１本買いました。

BACK INTO ENGLISH

I went to the store and bought a bottle of milk.