YOU SAID:

i was walking and than i foumd 10 dollars

INTO JAPANESE

歩いていたら10ドルを見つけた

BACK INTO ENGLISH

I found 10 dollars while walking.

INTO JAPANESE

歩いていたら10ドルを見つけました。

BACK INTO ENGLISH

As I was walking, I found $10.

INTO JAPANESE

歩いていると10ドルを見つけました。

BACK INTO ENGLISH

As I was walking, I found $10.