Firebase Function to send Notification

I have the following index.js and I want to create a function in order to send a notification to all my users.
When I deploy my function I get the error TypeError: functions.region is not a function. How can I change the region of my function and being able to deploy it

 const functions = require('firebase-functions');
 const admin = require('firebase-admin');
 const regionalFunctions = functions.region('europe-west1');
 admin.initializeApp();

 exports.sendNotificationToAllUsers = regionalFunctions.https.onCall(async (data, context) => {
     // Optional: Check if the user calling the function is authenticated or has specific roles
     // if (!context.auth) {
     //   // Throwing an HttpsError so that the client gets the error details.
     //   throw new functions.https.HttpsError('unauthenticated', 'The function must be called while authenticated.');
     // }

     const title = data.title || 'Default Title'; // Get title from the data sent by the client, or use a default
     const body = data.body || 'Default Body'; // Get body from the data sent by the client, or use a default

     const message = {
         notification: {
             title: title,
             body: body,
         },
         data: {
             page: 'highlights',
             // All values in the 'data' payload MUST be strings
         },
         android: {
             priority: 'high',
             notification: {
                 sound: 'default',
             }
         },
         topic: 'all', // Sending to a topic that all users are subscribed to.
         // Or, you can use 'android_users' if you want to target only Android users
         // and they are subscribed to that specific topic.
     };

     try {
         const response = await admin.messaging().send(message);
         console.log('Successfully sent message:', response);
         return {
             success: true,
             message: 'Notification sent successfully to all users.',
             messageId: response
         };
     } catch (error) {
         console.error('Error sending message:', error);
         // Throwing an HttpsError so that the client gets the error details.
         throw new functions.https.HttpsError('internal', 'Error sending notification.', error);
     }
 });

node -v v22.15.1
npm -v 10.9.0

The problem in your code lies here:

const functions = require('firebase-functions');
//                                          👆

In order to make it work, you need to specify the version:

const functions = require('firebase-functions/v1'); //See the /v1 import?
//                                           👆

Now you'll be able to deploy v.1 functions and use the corresponding region.