Short of downloading the Firefox source code myself, doing what must be done to import it into my favorite IDE (which may not be yours), and writing you a tutorial on how to repeat it, I suggest the following:

The following link (and others branching from there) contains very useful information. It doesn't contain the specific answer to your question, but gets you to a good starting point.

Unpack the source code you've downloaded and read the readme file. That file will probably give you build instructions which I don't think you want, but it may contain other useful info.

After reviewing the readme file, look for the source code files in the unpacked archive's directory structure. The source file directories may jump out at you, they may not, but you should be able to find them. There may also be header files located in separate directories. You might also look for a file that already defines the project in a way your IDE will understand, but I'm doubtful you'll find that.

The link above talked about access to the source code through a source control service. I don't know about those, but perhaps that's an attractive option for someone with your intentions.

Once you've figured out where the source and header files are, import them into a project you've created in your favorite and appropriate IDE. I like Eclipse's import feature, but I've only used it for my own small files that I've started elsewhere.

I suggest you start with a similar task on a smaller scale. Since you're (apparently) relatively unfamiliar with the IDE you'll be using for this graduate-level project, I suggest becoming more familiar with it, accomplishing similar tasks but on a smaller scale rather than jumping right to a project of Firefox' size and complexity. But that's how I would do it, probably not how you would do it.

None of this is rocket science. It is grunt work, manual labor. It'll take some time and effort. Report back to let us know how it's going and what you've had to do.