After I installed Windows 10 I lost all my previous programs. How do I recover all my tax programs and other programs which were on Windows 8.1

Did you perform an upgrade or did you perform a full, clean installation? If you ran a full installation, you will lose your applications and even your data unless you backed up your data. During an upgrade, all compatible programs will be migrated into Windows 10. 

Normally after an upgrade, there should be a folder on your desktop with the transferred files in there. There will also be a folder in Windows Explorer called Windows.old. Take a look at Retrieve files from the Windows.old folder which can help you with that. In order to see all of the files in the Windows.old folder, you may have to select show hidden files.