It's just the Wordpress upgrade process. The directions at wordpress.org walk you right through it.
I saw in your other post that you already deleted your database? If you did that, without backing it up, then you might as well just delete everything and do a fresh install if you're not sure what went wrong--since saving the data would have been the important step.
If you did any custom work, you might want to save that first. You could just save the whole directory to your computer and pick out any pieces you need later, once you're back up and running.
If you do the clean install, just make sure the folder is empty (including the .htaccess file), then just install it through the one-click-install menu in the control panel. Then you can just choose one of your existing DBs, or create another one during the setup.
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