In theory, yes. In practice; no, except maybe on a temporary basis; depending on how your mind works.

On a conceptual level, you need to discover how the two modules come together to form one or more logical units.

Then you need to take the code that comprises each one of those logical units, turn each logical unit into it's own distinct module.

Some people might find it's easier to put all the code together into one file while trying to sort out how the code works together; other people don't mind bouncing back and forth from file to file.

So, it's not a bad first step; but as chromatic points out, it shouldn't be your final step.