Not enough Space

Okay so this is my third week trying to download The Sims 3 Complete Collection and this is what is happening. I've been using a combo of this & this. I downloaded the base game and then applied the manual patch but now I am trying to download the World Adventure expansion and I am trying to turn it into a .dmg and then i get this error.




What gives? There is plenty of free space on my hard drive and I emptied my trash and even tried going into the terminal to turn off Time Machine backups or whatever. I have also went inside the file and tried to bring all of them into the into the disk but the same error shows up. I just keep running into problems!  Someone help, I'm so confused.