$wpdb is not initiating

You have written $wpdb incorrectly (3x) in your code example. If it is an exact copy it will never work. And you have a space in your SQL after prefix.’ which shouldn’t be there. And ‘From’ shoul dbe all caps.

Try this:

global $wpdb;
$sql="SELECT * FROM " . $wpdb->prefix . 'my_first_plugin';
$result = $wpdb->get_results($sql);