How to convert a mysqli query to $wpdb in wordpres

I want to use $wpdb query instead of mysqli for my wordpress table.

The wordpress table in question as follows : wp_example

+----+---------------------+------+
| id | name                | age  | 
+----+---------------------+------+
|  1 | Sandy Smith         | 21   |       
|  2 | John Doe            | 22   |        
|  3 | Tim Robbins         | 28   |         
|  4 | John Reese          | 29   |          
|  5 | Harold Finch        | 20   |       
+----+---------------------+------+

The mysqli query which I would like to be in $wpdb:

<?php
 // Make a MySQL Connection

$query = "SELECT * FROM wp_example";
$result = $mysqli->query($query);
$row = $result->fetch_array(MYSQLI_ASSOC);
printf ("%s (%s)\n", $row["name"], $row["age"]);

/* close connection */
?>

Reference 1
Reference 2

I started out to try something on my own but got stuck.

global $wpdb;
$query = $wpdb->get_results($wpdb->prepare("SELECT * FROM wp_example", ARRAY_A));

would love to have further guidance.

In your theme's functions file, add this:

function test_query() {
    // Global in the database
    global $wpdb, $table_prefix;
    // Set up the table name, ensuring you've got the right table prefix
    $table = $table_prefix . 'example';
    // For demo purposes, set up a variable
    $age = 21;
    // For TESTING ONLY, turn on errors to be sure you see if something goes wrong
    $wpdb->show_errors();
    // Use $wpdb->prepare when you need to accept arguments
    // Assign the query to a string so you can output it for testing
    $query = $wpdb->prepare( "SELECT * FROM {$table} WHERE age = %d", $age );
    // For TESTING ONLY, output the $query so you can inspect for problems
    var_dump( $query );
    // Get the results
    $results = $wpdb->get_results( $query );
    // Output the results
    foreach( $results AS $row ) {
        // Don't use ARRAY_A - just access as an object
        echo '<p>' . $row->name . '</p>';
        echo '<p>' . $row->age . '</p>';
    }
}

// Run your function
test_query();