YOU SAID:

I am going to go to the store today and buy an apple

INTO JAPANESE

今日は店に行ってリンゴを買う予定です

BACK INTO ENGLISH

I'm going to go to the store today to buy apples.

INTO JAPANESE

今日はリンゴを買いに店に行くつもりです。

BACK INTO ENGLISH

I'm going to go to the store to buy apples today.

INTO JAPANESE

今日は、リンゴを買いに店に行くつもりです。

BACK INTO ENGLISH

I'm going to go to the store to buy apples today.