Open the [Clone Phone] app, select [This is the new device] and then select the type of the old phone. A QR code is displayed in the upper part of the screen for connecting.
Open the [Clone Phone] app on the old phone, select [This is the old device] and scan the QR code on the new phone screen. The two phones will be connected.
Log in to iCloud of the iOS device, and enable synchronization options such as [Contacts] and [Photos] in iCloud as required. Open the [Clone Phone] app on the OnePlus phone, select [This is the new device] and then select the type of the old phone as iPhone.
Open [Clone Phone] on the iOS device, select [This is the old device] and then select the data you want to migrate. Use iOS device to scan the QR code in the OnePlus phone screen to connect the devices. Select [Start migration] to migrate the data.
To back up data to the cloud, you can go to [Settings] - [System settings] - [Back up and reset] - [Back up & migrate] - [Cloud backup]. Then select a type of data to be backed up, and tap [Start Backup]. You can back up your contacts, message, call logs, photos, audio files, documents and system data (Home screen layout and more) to the cloud.
Open [Clone Phone], and go to [This is the new device] - [Cloud backup]. You can select the backups you want to restore. Then select the types of data to be restored , and tap [Start].