You are referring to the Quick Start method. This method requires minimum of iOS version 12.4.x on your iPhone 6 Plus. You have iOS version 12.5.2 so you are good to use this method. I will list both options to accomplish what you want, below:
Transfer Data from old iPhone to new-
Do you have a backup created either on iCloud or on your computer?
Method 1 - Backup your old iPhone on your computer like this ➔ How to back up your iPhone, iPad, and iPod touch - Apple Support and then Restore your new iPhone from that backup like this ➔ Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Method 2 - The Quick Start method and here is how to do that ➔ Use Quick Start to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support
Axel F.