I found the solution by myself, I leave it here in case someone is interested:
<?php $args = array(
'post_type' => 'agrupados',
'tax_query' => array(
array(
'taxonomy' => 'pedidos',
'field' => 'slug',
'terms' => 'ferrol',
),
),); $the_query_slide = new WP_Query( $args ); if ( $the_query_slide->have_posts() ) {while ( $the_query_slide->have_posts() ) {$the_query_slide->the_post();?>
<?php
/* variables para cada imagen */
$full = get_the_post_thumbnail_url(get_the_ID(),'full');
$large = get_the_post_thumbnail_url(get_the_ID(),'large');
$medium = get_the_post_thumbnail_url(get_the_ID(),'medium');
$thumbnail = get_the_post_thumbnail_url(get_the_ID(),'thumbnail');
?>
<div class="col col-md-flex-6 col-lg-flex-3 ">
<picture class="cat-agrupados-img">
<source media="(min-width: 768px)" srcset="https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/https://wordpress.stackexchange.com/<?php echo esc_url($thumbail); ?>">
<img src="https://wordpress.stackexchange.com/questions/320836/<?php echo esc_url($medium);?>" alt="<?php the_title(); ?>">
</picture>
<h2 class="cat-agrupados-titulo-pedido">Pedido agrupado en <?php the_title(); ?></h2>
<p class="cat-fecha-publicacion">Fecha de publicación: <strong><?php the_date(); ?></strong></p>
<p class="cat-agrupados-zona">Zonas: <strong><?php echo get_post_meta( get_the_ID(), 'yourprefix_agrupados_poblaciones', true ); ?></strong></p>
<a href="<?php the_permalink(); ?>" class="cat-agrupados-link">Ver pedido agrupado</a>
</div> <!--cierre columna-->
<?php }} wp_reset_postdata(); ?>