Get post from meta_key and meta_value

You can get using this using SQL

global $wpdb;

// For single record
$wpdb->get_row("SELECT post_id FROM $wpdb->postmeta WHERE meta_key = $param1 AND meta_value = $param2");

// For multiple records
$wpdb->get_results("SELECT post_id FROM $wpdb->postmeta WHERE meta_key = $param1 AND meta_value = $param2" );

Use this for query

 $args = array(
        'posts_per_page' => 10, // -1 for all posts
       'meta_query' => array(
           array(
               'key' => 'your_meta_key',
               'value' => 'your_meta_value',
               'compare' => '=',
           )
       )
    );
    $the_query = new WP_Query($args);

// The Loop
if ( $the_query->have_posts() ) {
    echo '<ul>';
    while ( $the_query->have_posts() ) {
        $the_query->the_post();
        echo '<li>' . get_the_title() . '</li>';
    }
    echo '</ul>';
    /* Restore original Post Data */
    wp_reset_postdata();
} else {
    // no posts found
}