As said in comments, you should use meta_query
.
For help on how to query posts by ACF meta field, you can check the ACF documentation:
https://www.advancedcustomfields.com/resources/query-posts-custom-fields/
$args = array(
'numberposts' => -1,
'post_type' => 'event',
'meta_key' => 'location',
'meta_value' => 'Melbourne'
);
// query
$the_query = new WP_Query( $args );