I think you have misunderstand the process.
000webhost and hostinger are two companies. The “upgrade” option redirect you to hostinger. If you bought a premium hosting at hostinger on black friday sales, you have upgraded. Now go to cpanel.hostinger.com and login there.
Then set up your hosting account. There should be an option to
import 000webhost site to hostinger. If so, click that and continue.
If you coudn’t find that, just set up your hosting account without doing anything. Then contact their live support (the button in the bottom right corner) and ask them to import your website to hostinger.
If you have any other questions, reply here