Hi, I need to know the purchase date of my I phone 6+

The iPhone 6+ was released by Apple in 2014, and discontinued in 2016.

You may purchase replacement charging adapter and/or cable.

Lightning to USB Cable (1 m) - Apple

Apple 12W USB Power Adapter - Apple

It’s on your sales receipt. There is not another way to know the exact date.

Why? It is WAY out of warranty now.