Get product number and lookup in google sheet and then redirect the user to the target product url.

product_lookup_fluentform.php

<?php

/*
 * Catch submission the before it's inserting in database
 * if you want to log the data in the database use hook: fluenform_before_submission_confirmation
 */
add_action('fluentform_before_insert_submission', function ($insertData, $data, $form) {
    if($form->id != 156) { // 156 is our target form id
        return;
    }
    $csvUrl = 'https://docs.google.com/spreadsheets/d/e/2PACX-1vRENwqlrjjveVU-E-LANfPiMIsuTvdXqVVd0FGKTldEyrPnmF_tsjOYeV-4Q-qh5qqH9-NpYN44FH4r/pub?gid=0&single=true&output=csv';
    $matchedColumnIndex = 0; // 0 is the first column of the csv
    $inputName = 'product_id'; // 'product_id' is the name attribute of the input

    $row = ffeGetMatchedRow($csvUrl, $data[$inputName], $matchedColumnIndex);
    if(!$row) {
        // We could not find the product so send an error message
        wp_send_json(['errors' => [
            $inputName => ['Sorry! No Product Found with this number']
        ]], 422);
    }

    $productUrl = $row[1]; // We have product URL at the 2nd column so index is 1;

    if(!$productUrl || filter_var($productUrl, FILTER_VALIDATE_URL) === FALSE) {
        // Not a valid URL
        wp_send_json(['errors' => [
            $inputName => ['Sorry! No Valid Product URL found']
        ]], 422);
    }

    wp_send_json_success([
        'result' => [
            'redirectUrl' => $productUrl,
            'message' => 'You are redirecting to the product page',
        ]
    ], 200);

}, 10,3);

/*
 * Helper function will return the matched column value for the provided csv url
 * Please note, You need Fluent Forms Pro to make it work
 */
function ffeGetMatchedRow($csvUrl, $value, $columnIndex)
{
    if (!class_exists('CSVParser')) {
        require_once(FLUENTFORMPRO_DIR_PATH . 'libs/CSVParser/CSVParser.php');
    }
    $csvParser = new \CSVParser;
    $content = file_get_contents($csvUrl);
    $csvParser->load_data($content);
    $rows = $csvParser->parse($csvParser->find_delimiter());
    if(!$rows) {
        return false;
    }
    array_shift($rows); // remove the first item

    foreach ($rows as $row) {
        if(!empty($row[$columnIndex]) && $row[$columnIndex] == $value) {
            return $row;
        }
    }

    return false;
}