YOU SAID:

i need to go to the store to get lemons

INTO JAPANESE

私はレモンを手に入れるために店に行く必要があります

BACK INTO ENGLISH

I have to go to the store to get the lemon

INTO JAPANESE

私はレモンを手に入れるために店に行かなければなりません

BACK INTO ENGLISH

I have to go to the store to get the lemon