You don't seem to have a trigger for your JS. You can test that the script is actually running by adding a quick console, such as

console.log('xyz.js is running');

Once you're sure your JS is running, you can add a trigger. If you're already loading jQuery, it has an easy .ready() function to use, but if not, there are other ways.

It's also best practice to enqueue your JavaScript, instead of adding <script> tags directly. See wp_enqueue_script(). You may want to do this before adding your console and before adding the trigger, as really enqueueing is the first step.

It seems like you're trying to use PHP inside a JS file, which won't work. Instead, you'll need to pass the dynamic path to your JS file from PHP using wp_localize_script() which can be used on enqueued and registered scripts like this:

function custom_enqueue_script() {
    wp_enqueue_script(
        'custom-xyz', // Handle
        get_template_directory_uri() . '/xyz.js',
    );
    wp_localize_script(
        'custom-xyz', // Handle
        'my_object', // Object variable name
        array('theme_dir' => get_template_directory_uri()) // Properties and values
    );
}
add_action('wp_enqueue_scripts', 'custom_enqueue_script');

And then in the xyz.js file, the my_object is an object variable available to you.

document.getElementById("load").src = my_object.theme_dir + "/Images/pic.png";