functions.php

add_action( 'template_redirect', 'wc_custom_redirect_after_purchase' );
function wc_custom_redirect_after_purchase() {
    global $wp;

    if ( is_checkout() && ! empty( $wp->query_vars['order-received'] ) ) {
    	$order_id = absint( $wp->query_vars['order-received'] );
        wp_redirect( get_permalink( {PAGE_ID} ) . '?order=' . $order_id );
        exit;
    }
}