How to customize the user search

Hello!
I’m developing a custom user search and I’m using this plugin found here:

`<?php

function sul_user_listing($atts, $content = null) {
global $post;

extract(shortcode_atts(array(
“role” => ‘technician’,
“number” => ’10’
), $atts));

$role = sanitize_text_field($role);
$number = sanitize_text_field($number);

// We’re outputting a lot of HTML, and the easiest way
// to do it is with output buffering from PHP.
ob_start();

// Get the Search Term
$search = ( isset($_GET[“as”]) ) ? sanitize_text_field($_GET[“as”]) : false ;

// Get Query Var for pagination. This already exists in WordPress
$page = (get_query_var(‘paged’)) ? get_query_var(‘paged’) : 1;

// Calculate the offset (i.e. how many users we should skip)
$offset = ($page – 1) * $number;

if ($search){
// Generate the query based on search field
$my_users = new WP_User_Query(
array(
‘role’ => $role,
‘search’ => ‘*’ . $search . ‘*’,
));
} else {
// Generate the query
$my_users = new WP_User_Query(
array(
‘role’ => ‘technician’
));
}

// Get the total number of authors. Based on this, offset and number
// per page, we’ll generate our pagination.
$total_authors = $my_users->total_users;

// Calculate the total number of pages for the pagination
$total_pages = intval($total_authors / $number) + 1;

// The authors object.
$authors = $my_users->get_results();
?>

<style>

.advance-search .real-btn {
margin: 0;
}

</style>

<section class=”advance-search “>
<form method=”get” id=”sul-searchform” class=”advance-search-form clearfix” action=”<?php the_permalink() ?>”>
<div class=”option-bar small”>
<input type=”text” class=”field” name=”as” id=”sul-s” placeholder=”Cerca tecnico” />
</div>
<div class=”option-bar”>
<input type=”submit” name=”submit” class=” real-btn btn” id=”sul-searchsubmit” value=”Cerca” />
</div>
</form>
<?php
if($search) { ?>
<h2>Ricerca: <em><?php echo $search; ?></em></h2>
<!–<a>”>Back To Author Listing</a>–>
<?php } ?>

</section><!– .author-search –>

<?php if (!empty($authors)) { ?>
<ul class=”author-list”>
<?php
// loop through each author
foreach($authors as $author) {
$author_info = get_userdata($author->ID);
?>

<li>
<?php if(!empty($author->pie_profile_pic_5)): ?>
<img width=”130″ height=”130″ src=”<?php echo $author->pie_profile_pic_5; ?>”
class=”attachment-agent-image wp-post-image” alt=”<?php echo $author->first_name; ?> <?php echo $author->last_name; ?>”>
<h2 style=”display: inline; margin-left: 20px;”>
<a>ID); ?>”><?php echo $author->first_name; ?> <?php echo $author->last_name; ?></a>
– <?php echo count_user_posts( $author->ID ); ?> immobili
</h2>
<?php else: ?>
<h2 style=”display: inline;”>
<a>ID); ?>”><?php echo $author->first_name; ?> <?php echo $author->last_name; ?></a>
– <?php echo count_user_posts($author->ID, “property”); ?> immobili
</h2>
<?php endif; ?>

<p><?php //echo $author_info->description; ?></p>
<?php $latest_post = new WP_Query( “author=$author->ID&post_count=1” );
if (!empty($latest_post->post)){ ?>
<p><strong>Latest Article:</strong>
<a>post->ID) ?>”>
<?php echo get_the_title($latest_post->post->ID) ;?>
</a></p>
<?php } //endif ?>
<!–<p><a>ID); ?> “>Maggiori informazioni.. <?php //echo $author_info->display_name; ?></a></p>–>
</li>
<?php
}
?>
<!– .author-list –>
<?php } else { ?>
<!–<h2>Nessun tecnico trovato</h2>–>
<? } //endif ?>

<nav id=”nav-single” style=”clear:both; float:none; margin-top:20px;”>
<!–<h3 class=”assistive-text”>Post navigation</h3>–>
<?php if ($page != 1) { ?>
<span class=”nav-previous”><a rel=”prev”>page/<?php echo $page – 1; ?>/”><span class=”meta-nav”>←</span> Previous</a></span>
<?php } ?>

<?php if ($page < $total_pages ) { ?>
<span class=”nav-next”><a rel=”next”>page/<?php echo $page + 1; ?>/”>Next <span class=”meta-nav”>→</span></a></span>
<?php } ?>
</nav>

<?php
// Output the content.
$output = ob_get_contents();
ob_end_clean();

// Return only if we’re inside a page. This won’t list anything on a post or archive page.
if (is_page()) return $output;

}

// Add the shortcode to WordPress.
add_shortcode(‘userlisting’, ‘sul_user_listing’);
?>`

But I want to expand the search by city, state and country.
In fact, inside the wp_usermeta table has these values:
meta_key: pie_address_3;
meta_value: a:6:{s:7:"address";s:18:"New York Street, 4";s:8:"address2";s:0:"";s:4:"city";s:5:"Venice";s:5:"state";s:7:"Vicenza";s:3:"zip";s:5:"36015";s:7:"country";s:5:"Italy";}

Thus, my question is: how can expand the search using these meta values?
Thanks!