Installing Parallels On External HD for Snow Leopard on Mac Running 10.9.5

So I am trying to run Pro Tools 9 but my mac updated to later OS that it doesn't run on now, so I installed Parallels and ran snow leopard from it but I'm getting an error message saying my mac doesn't have enough RAM to run snow leopard from the virtual machine. I bought an external HD with 1 terabyte of storage and dragged the parallels icon from my documents to the external HD, then double clicked thinking it would run parallels from the external HD now with more space and not have the RAM issue, but I'm getting the same error message, I don't know a lot about this, what am I doing wrong?

RAM is not storage, it's memory. Drives have nothing to do with it. How much memory did you configure for the virtual machine when you created it?