Can I replace “in” with “to” or "for"? I don’t know how to use "in" here.
Native speaker’s answer
Rebecca
"In" is used in this case because it goes with the idiomatic phrase, "in search of", which means that someone is in the process of searching for something. You can replace "in" with "to" if you change the sentence to "to search for gold". Here's a few more examples: Ex: I am in search of a new job. Ex: I am searching for a new job. The first example in this case is an idiomatic phrase, but expresses the same meaning as the second example.