Add Metabox to Portfolio item

I use the function below to add a metabox to posts, which word fine.
I want this box in enfold portfolio items too, but can´t figure out how to do.

function prfx_custom_meta() {
    add_meta_box( 'prfx_meta', __( 'Featured Post Startseite', 'prfx-textdomain' ), 'prfx_meta_callback', $screen = array("post"));
}
add_action( 'add_meta_boxes', 'prfx_custom_meta' );

/**
 * Outputs the content of the meta box
 */
function prfx_meta_callback( $post ) {
    wp_nonce_field( basename( __FILE__ ), 'prfx_nonce' );
    $prfx_stored_meta = get_post_meta( $post->ID );
    ?>

 <p>
    <span class="prfx-row-title"><?php _e( 'Post in Homepage Karusell', 'prfx-textdomain' )?></span>
    <div class="prfx-row-content">
        <label for="homepage">
            <input type="checkbox" name="homepage" id="homepage" value="1" <?php if ( isset ( $prfx_stored_meta['homepage'] ) ) checked( $prfx_stored_meta['homepage'][0], '1' ); ?> />
            <?php _e( 'anzeigen', 'prfx-textdomain' )?>
        </label>

    </div>
</p>
<p>
    <span class="prfx-row-title"><?php _e( 'Sortierung', 'prfx-textdomain' )?></span>
    <div class="prfx-row-content">
        <label for="meta-radio-one">
            <input type="radio" name="sortierung" id="meta-radio-1" value="1" <?php if ( isset ( $prfx_stored_meta['sortierung'] ) ) checked( $prfx_stored_meta['sortierung'][0], '1' ); ?>>
            <?php _e( '1', 'prfx-textdomain' )?>
        </label>
        <label for="meta-radio-one">
            <input type="radio" name="sortierung" id="meta-radio-2" value="2" <?php if ( isset ( $prfx_stored_meta['sortierung'] ) ) checked( $prfx_stored_meta['sortierung'][0], '2' ); ?>>
            <?php _e( '2', 'prfx-textdomain' )?>
        </label>
        <label for="meta-radio-one">
            <input type="radio" name="sortierung" id="meta-radio-3" value="3" <?php if ( isset ( $prfx_stored_meta['sortierung'] ) ) checked( $prfx_stored_meta['sortierung'][0], '3' ); ?>>
            <?php _e( '3', 'prfx-textdomain' )?>
        </label>
        <label for="meta-radio-one">
            <input type="radio" name="sortierung" id="meta-radio-4" value="4" <?php if ( isset ( $prfx_stored_meta['sortierung'] ) ) checked( $prfx_stored_meta['sortierung'][0], '4' ); ?>>
            <?php _e( '4', 'prfx-textdomain' )?>
        </label>
        <label for="meta-radio-two">
            <input type="radio" name="sortierung" id="meta-radio-5" value="5" <?php if ( isset ( $prfx_stored_meta['sortierung'] ) ) checked( $prfx_stored_meta['sortierung'][0], '5' ); ?>>
            <?php _e( '5', 'prfx-textdomain' )?>
        </label>
    </div>
</p>	

    <?php
}

/**
 * Saves the custom meta input
 */
function prfx_meta_save( $post_id ) {
 
    // Checks save status
    $is_autosave = wp_is_post_autosave( $post_id );
    $is_revision = wp_is_post_revision( $post_id );
    $is_valid_nonce = ( isset( $_POST[ 'prfx_nonce' ] ) && wp_verify_nonce( $_POST[ 'prfx_nonce' ], basename( __FILE__ ) ) ) ? 'true' : 'false';
 
    // Exits script depending on save status
    if ( $is_autosave || $is_revision || !$is_valid_nonce ) {
        return;
    }

// Checks for input and saves if needed
if( isset( $_POST[ 'sortierung' ] ) ) {
    update_post_meta( $post_id, 'sortierung', $_POST[ 'sortierung' ] );
    
    
}
   
// Checks for input and saves
if( isset( $_POST[ 'homepage' ] ) ) {
    update_post_meta( $post_id, 'homepage', '1' );
} else {
    update_post_meta( $post_id, 'homepage', '' );
}
 
}

add_action( 'save_post', 'prfx_meta_save' );