YOU SAID:

i was going down to the dairy to buy milk

INTO JAPANESE

私は牛乳を買うために乳製品に行くつもりだった

BACK INTO ENGLISH

I was going to go dairy to buy milk.

INTO JAPANESE

私は牛乳を買うために乳製品に行くつもりでした。

BACK INTO ENGLISH

I was going to go dairy to buy milk.