In which word form does 探し belong to?


I confuse with usage of 探し in this sentence:

> 探しに行くんだ そこへ

I have tried to google it. But they show me 探す which is a u-verb. And I am
unable to find _sagashi_. The closest one is _sagashita_ which is its past
form. It is a type of clipping such as "chemistry" becomes "chem" or what?

My question is: in what form _sagashi_ is and when to use it?

