"I must find them" 可以用英语表达为 "I have to find them" 或 "I need to find them"。其中 "must" 是一个表示"必须"的助动词，"have to" 和 "need to" 都是表示"必须"的情态动词。
例句：
I must find my keys before I leave the house. (我必须在离开房子前找到我的钥匙。)
I have to find a new job soon. (我必须很快找到一份新工作。)
I need to find a way to solve this problem. (我必须找到解决这个问题的方法。)