看不懂这句Samson says that is when he came up with the idea of changing the waste into so...

看不懂这句Samson says that is when he came up with the idea of changing the waste into so...

这是多重复合句。

第一重
〔主句〕Samson says
〔宾语从句〕that is when he came up with the idea of changing the waste into something useful

第二重
〔嵌套主句〕that is
〔嵌套表语从句〕when he came up with the idea of changing the waste into something useful

参考译文：萨姆森说那就是他什么时候提出来把废物变成有用东西这种想法。

Samson says 主语+谓语 that is：宾语 when he came up with the idea of changing the waste into useful ：强调状语
come up with：
想出；提出。
全句的意思是：
山姆桑说，正是那个时候他提出了变废为宝的想法。