YOU SAID:

if you walked all the way to japan then you would be a car

INTO JAPANESE

日本まで歩いたら車になります

BACK INTO ENGLISH

If you walk to Japan, you will be in a car

INTO JAPANESE

日本に行くと車に乗る

BACK INTO ENGLISH

Get in a car when you go to Japan

INTO JAPANESE

日本に行くときは車に乗る

BACK INTO ENGLISH

Get in the car when you go to Japan

INTO JAPANESE

日本に行くときは車に乗りなさい

BACK INTO ENGLISH

Get in the car when you go to Japan