When I found this birthday card, it reminded me of the picture you draw when you were a child.
このカードを見つけた時子供の頃に描いた絵を思い出した
この誕生カード this birthday card
~を見つけたとき when I found ~,
~を思い出した、~を思い出させる A remind(s) B of C
AがBにCのことを思い出させる。
When I found this birthday card, it reminded me of the picture you draw when you were a child.