The main page loads, but all friendly URL's are showing the error. This points to your .htaccess file being missing.
You'll need to visit the ACP -> Search Engine Optimization page and download the htaccess file that's linked there.
Then you need to upload that file to the root folder (assuming one is not already present; if one is already there, see below) and make sure it is named .htaccess (note the leading period).
If that file is already present, you need to edit it, and add the lines in the file you downloaded from the ACP, then save it.
Does that resolve those errors?