date_query won’t accept day parameter, but will accept month and year for a custom post

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 );