Hi ​@MCL1 ,

Great news, you don’t need to wait for the number switch to finish before setting up your new iPhone!  You can go ahead and transfer all your apps, messages, and account details now using Quick Start or iCloud backup. Everything will move over safely.
Once the number switch is complete, your new phone will automatically update with your correct number, so you won’t lose any messages or data. Just make sure you sign in with your Apple ID during setup
How to Transfer Your Data to Your New iPhone
 

Option 1: Quick Start (Fast & Easy)

Place both iPhones next to each other and turn on your new iPhone.
On your old iPhone, you’ll see a Quick Start screen—tap Continue.
Scan the animation on your new iPhone using your old iPhone’s camera.
Follow the on-screen steps to transfer your data.
Keep both devices connected to Wi-Fi and power until the process finishes.

 

Option 2: iCloud Backup

On your old iPhone, go to Settings > [Your Name] > iCloud > iCloud Backup.
Tap Back Up Now and wait for the backup to complete.
On your new iPhone, during setup, choose Restore from iCloud Backup.
Sign in with your Apple ID and select the latest backup.

After the number switch completes, your new iPhone will automatically update with your correct number.
No messages or apps will be lost!

Lamiya