Unable to complete data transfer error while transferring data

Hey there, ruchi33.

Thanks for reaching out to Apple Support Communities. We understand that you're having some issues transferring data. We're happy to provide some assistance.

We see that you came from the Use Quick Start to transfer data to a new iPhone, iPad, or iPod touch article, are you trying to set up a new device? If so, try resting both devices and transfer performing the Quick Start steps again:

Restart your iPhone

If the issue persists, you can also use an iCloud or iTunes/Finder backup to set up your new phone.

Use iCloud to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch

Use iTunes or Finder to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch

How to back up your iPhone, iPad, and iPod touch -- If you decide to use a backup to set up your new phone, be sure that the backup you're using is recent.

Let us know how that goes.

Take care.