Error establishing a database connection; After importing DB & Theme

The database password is not stored in the database itself, so importing the database via phpmyadmin will not also import the password. You need to manually edit your local copy of wp-config.php, and enter your local username and password for MySQL ( or any other database you are using ).

Usually the default username for local development installations is root, and the password is blank, so you can try these. Otherwise, you can check xampp’s website to see what the default password, or if you have already set your own password during installation, you can use that.