Redirect to Seperate Thank You Page For 2 or More Items

readme.txt

Use snippet wcrtpf2omi2.php if you don't want the snippet to handle redirection for single products. Replace the $thankyou_page_url and $thankyou_multiple_page_url variables with the URLs of your custom thank you pages as needed. 

wcrtpf2omi.php

function custom_thankyou_redirection() {
    global $woocommerce;
    $items_count = $woocommerce->cart->cart_contents_count;
    $thankyou_page_url = 'https://www.yourwebsite.com/thank-you/';
    $thankyou_multiple_page_url = 'https://www.yourwebsite.com/thank-you-multiple/';
    if ( $items_count >= 2 ) {
        wp_redirect( $thankyou_multiple_page_url );
        exit;
    } else {
        wp_redirect( $thankyou_page_url );
        exit;
    }
}
add_action( 'woocommerce_thankyou', 'custom_thankyou_redirection' );

wcrtpf2omi2.php

function custom_thankyou_redirection() {
    global $woocommerce;
    $items_count = $woocommerce->cart->cart_contents_count;
    if ( $items_count >= 2 ) {
        $thankyou_multiple_page_url = 'https://www.yourwebsite.com/thank-you-multiple/';
        wp_redirect( $thankyou_multiple_page_url );
        exit;
    }
}
add_action( 'woocommerce_thankyou', 'custom_thankyou_redirection' );