icloud

If the photos are in iCloud Photos (e.g., if you had iCloud Photos option turned on in your old phone), turn that option on in your new phone and they will automatically sync to it. See: Set up and use iCloud Photos - Apple Support

If you didn't have iCloud Photos turned on in your old phone but you do have an iCloud Backup of it, you can use the backup to setup your new phone. Note that this will replace any data (not just photos) that you may have added to your new phone since you bought it. See: iCloud: Restore or set up iOS devices from an iCloud backup