You'll recognize the world package because it got a WPID ressource. You will have to go through them and peek into the files with s3pe. It might be the biggest package file but then, especially in this case, it might not.
Now you have to sort through them and find the one that is actually the world. You will get a ton of package files with a world like New York CIty because it uses a ton of cc. Not all items you extract may work as intended (counters for example, some pattern etc.)
Also, with worlds that use lots of cc as the one you want to install it's quite tedious, too. I have to warn you though, this method requires knowledge of package files and how to use s3pe. If you want to make it a world file in order to avoid the launcher (as I do, too), you will need to unpack it with Delphy's Sims 3 Pack Multi-Extracter here: Yes, you would install it via launcher as any other sims3pack.
