“当我老的时候，我会回到中国，交一些世界各地的笔友”用英语翻译。

When I am old,I will back to China and make some pal friends of the whole world.

“when I am old, I will return to China, will hand over some world's pen pal”

When I am old, I will come back to China and make some pen pals from all over the world.

When I am old,I will return to China and make some worldwide pen pals.

i'll come back to china when i'm old,making pen-pals from all over the world

When i am old,i will go back to China and make some pen pals from all over the world.