Yes, you can download all of your iTunes purchases from the iTunes Store again for free. Go to iTunes Store>Purchased and download the content you want.
If you have content on your MacBook Pro that wasn't purchased from the iTunes Store, you will have to either physically copy them over using a hard drive or something, or subscribe to iTunes Match. iTunes Match will read your non-purchased content and replace it with equivalent (and perhaps higher-quality) content that has all the advantages of purchased content (as above). The remaining songs that iTunes could not find a match for in the iTunes Store will be uploaded to the cloud and be available for download, similar to the way you download previous iTunes Purchases. But I recommend just getting a hard drive and physically copying your content over.