YOU SAID:

I'm going to the store to pick up a gallon of milk.

INTO JAPANESE

私はその店に 1 ガロンの牛乳を取りに行きます。

BACK INTO ENGLISH

I go to the store to get a gallon of milk.

INTO JAPANESE

私は 1 ガロンの牛乳を買いに店に行きます。

BACK INTO ENGLISH

I go to the store to buy 1 gallon of milk.

INTO JAPANESE

私はその店に1ガロンの牛乳を買いに行きます。

BACK INTO ENGLISH

I go to the store to buy a gallon of milk.

INTO JAPANESE

私は 1 ガロンの牛乳を買いに店に行きます。

BACK INTO ENGLISH

I go to the store to buy 1 gallon of milk.

INTO JAPANESE

私はその店に1ガロンの牛乳を買いに行きます。

BACK INTO ENGLISH

I go to the store to buy a gallon of milk.