lost files in icloud

How can I restore my lost files in iCloud?

After updating my iMac 2014 to the latest Yosemite, my computer would not start. I was keeping results of my glucose in the cloud using my iPad and iMac. I could only get my iMac to work if I restored it using Time Machine. My records from September to December &December to March stayed saved in iCloud but my March to the present was lost. I had saved two copies in iCloud, one on iCloud and one in numbers on iCloud. Both are gone.