It's not possible to say " look someone up to" or " look up someone to" .

不可以说 " look someone up to" 或者 " look up someone to" 。

I need to look someone up in your archives.

我需要查查你们档案上的一个人。

" To look someone up" is a phrasal verb meaning to search for that person – usually, nowadays, in a database that is in a computer.

“查找某人”是一个短语动词，意思是搜索那个人——通常，现在，在计算机的数据库中。