How can I download songs that are stored on the cloud to my iPod? It downloaded only the recent songs purchased since I bought my iMac.

I have a fair number of songs that are on the cloud from when I bought them a year or two ago when I had another iMac. I've purchased about the same number of songs from iTunes since buying my present iMac. Today, I wanted to download all of my songs on an iPod Nano that I decide to re-synch with this new iMac, and it did download all of the songs I had purchased after buying my present iMac, but did not download any of the songs that are on the cloud. How do I go about downloading these songs?