On the old computer you would want to backup your data files. 

https://accountants-community.intuit.com/articles/1606223-how-to-copy-or-backup-client-files-using-p... shows you how to backup the returns. 

Bring your backup to the new computer. (The best way to do this is to use a Flash Drive). 

Then on the new computer, you would want to use Restore for each year. This article shows you how to Restore: 

https://accountants-community.intuit.com/articles/1606637-restoring-client-data-files-using-proserie...