How do I transfer Itunes purchases?

Hi,

I have a Macbook Pro, selling it as I don't really have any need for it anymore. I have backed up my photos and stuff but the thing I'm worried about is the Itunes content. My library is all purchased from the Itunes store and it's just under 15GB. My ipod isn't able to store all of my music but obviously I don't want to pay for them and not have access. I was wondering that if I signed into my Itunes account on another laptop/computer will I be able to redownload the content I purchased without paying? Or is there a way of moving it onto my Icloud account? I've tried to open it but there doesn't seem to be an option for my music despite what I've read online. I was just wanted to know if there was any way of doing this without having to buy an external hard drive and putting it on there.

Thanks in advance for the help!