ACF plugin stores data in the wp_postmeta like the default WordPress custom fields.
To get data from a custom field your code should look like this (assuming the custom field name is “brand_name”).
$title = get_the_title();
$the_query = new WP_Query( array(
'posts_per_page'=>9,
'post_type'=>'product_name',
'order' => 'ASC',
'meta_query' => array(
array( "key" => "brand_name", "value" => $title )
),
'paged' => get_query_var('paged') ? get_query_var('paged') : 1)
);
For more details on using meta fields in the WP_Query please see https://codex.wordpress.org/Class_Reference/WP_Query#Custom_Field_Parameters