A very basic iTunes Question - Help?!

Hi guys,

Hoping I can get some help here. I have an iTunes account, and a great deal of content (music, films, tv) on my old apple macbook pro. Maybe 50% of it was purchased on iTunes, the rest CD rips or downloads. I think the pro is about to die (its about 8-10 years old) and I am worried about losing all my content. I regularly back up using time machine. The question is about how I would get my content across to my new macbook air?

Thanks in advance.