get post id using custom filed value

Question

Try something like this

$posts = get_posts( array(
    'numberposts' => -1,
    'meta_key' => 'prime', 
    'meta_value' => 'yes' 
    ) );

$post_ids = array();

if ( $posts ) {
    foreach ( $posts as $post ) {
        // Push post's IDs into array
        array_push( $post_ids, $post->ID );
    }
}

code isn’t tested but it should work. If you don’t wont post ids into array just replace whole array_push line with $post->ID

UPDATE

Set ‘numberposts’ argument to -1, so it will return all posts not only 5 as default. Thanks to @Brady