GitHub search for code text in limited list of repositories

Question

In GitHub I want to search for certain references in code inside a limited set of repositories.

I have this GitHub query, and it gives me what I want in terms of the repos I want to search in:

org:MYORG repo.name.partial in:name type:Repositories

Now I'd like to add another parameter to now search the code within that limited set. But what I have tried doesn't work.

I tried placing my search term at the end like this:

org:MYORG repo.name.partial in:name type:Repositories find_this_in_code

But it doesn't work. 0 Results. But I know what I'm searching for exists.

I've looked in the search docs, but I can't see a parameter to add to search in code under this circumstance.

Appreciate some advice or direction.

Thanks