@Marko Krunic since you've just migrated to a new server, and as @Daniel F said above your problem is with SQL connection. You must setup the same username and password form the SQL connection you were using on old server, and it must have permission to the same database name you are using.
You can get those information from conf_global.php
$INFO = array (
'sql_host' => 'localhost',
'sql_database' => 'databasename',
'sql_user' => 'username',
'sql_pass' => 'password',