Issue with Me and My Katamari PSP extraction. HELP

[Hellaciousness]

So, I just downloaded Me and My Katamari for use on my hacked PSP, and when I extracted the RAR files, all I saw were 50 or so rar part files, but lacked a rar file to click and extract them all to an iso. I clicked on one of the part rar files, kept getting error messages about a broken file or something, and it created an incomplete iso. So, I highlighted all of the files and tried extracting them, everytime got the same error message and more and more incomplete isos. Normally, I can just click on one of the files in the folder and it makes on clean iso, but this is the first time I have come across this issue. I use The Unarchiver program for extraction on the mac btw. Am I doing something wrong or is this a problem with the file itself? PLZ HALP!

EDIT: Also, I tried to make an iso from the entire folder of rar parts, only got corrupted file when I put it on the PSP.