Upgrading to a new OS comes with a set of challenge. The first being figuring out where everything is: “When I downloaded System 10, it did not download my contacts list. Therefore, I can’t send any e-mails. Thank you for any help.”
As long as you did an upgrade and not a clean install, your contacts should be right where you left them. You don’t say which program you were using to send emails, but your contacts should still bet there and untouched. If you were accessing your email on a website, you should be able to open a browser, go to that site and find them where you left them.
If you were using an email client like Outlook, Thunderbird, or Windows Live Mail installed on your PC – just open that program up. If you don’t see the icon right away, type the name in the search box and click on the search results.
If you’re using the new Windows Mail app included in Windows 10, it imports the contacts that you have set on the web interface for your email accounts when you link the accounts to the app.