how i can fix this error?! : Uncaught ReferenceError: THREE is not defined

I created a subdomain inside the host and inside this subdomain I created a folder and created an index file to call the threejs code, which is my code:

    <script>  
        // صحنه، دوربین و رندرکننده را ایجاد کنید  
        const scene = new THREE.Scene();  
        const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);  
        const renderer = new THREE.WebGLRenderer();  
        renderer.setSize(window.innerWidth, window.innerHeight);  
        document.body.appendChild(renderer.domElement);  

        // نور به صحنه اضافه کنید  
        const light = new THREE.AmbientLight(0xffffff);  
        scene.add(light);  

        // دراکو بارگذار و GLTFLoader را تنظیم کنید  
        const dracoLoader = new THREE.DRACOLoader();  
        dracoLoader.setDecoderPath('/examples/jsm/libs/draco/');  
        const loader = new THREE.GLTFLoader();  
        loader.setDRACOLoader(dracoLoader);  

        // بارگذاری مدل GLTF  
        loader.load(  
            'https://demo.arendlighting.com/arsalan/object/scene.gltf',  
            function (gltf) {  
                scene.add(gltf.scene);  
                gltf.scene.position.set(0, 0, 0); // موقعیت مدل  
            },  
            function (xhr) {  
                console.log((xhr.loaded / xhr.total * 100) + '% loaded');  
            },  
            function (error) {  
                console.log('An error happened:', error);  
            }  
        );  

        // تنظیم دوربین  
        camera.position.z = 5;  

        // حلقه رندر  
        function animate() {  
            requestAnimationFrame(animate);  
            renderer.render(scene, camera);  
        }  
        animate();  

        // تنظیم اندازه‌گیری صفحه  
        window.addEventListener('resize', function() {  
            camera.aspect = window.innerWidth / window.innerHeight;  
            camera.updateProjectionMatrix();  
            renderer.setSize(window.innerWidth, window.innerHeight);  
        });  
    </script>  
</body>  
</html>`

But when I run the browser page, I encounter a white screen and it shows me this error in the console: Uncaught ReferenceError: THREE is not defined.
What is wrong?!

i try in this link : https://demo.arendlighting.com/arsalan/
PlZz heeeeelppp me…