How to find out the speed of my phone and the cellular data on my I phone 6 plus

I'm guessing, but when you are asking for the speed of the phone you are referring to download and upload speeds when you are on cellular data? If that is the case, you can search the App Store for any applications that measure that information. Speedtest by Ookla is one, it is free and when connected to cellular data it will perform a test and provide you with information.

As ChrisJ4203 said, Speedtest is a great app but if you don't want to install apps, use Safari browser to visit https://fast.com (warning: internet speed test will start immediately when you visit the website). It only measures downstream speed. There's no upstream test.

Thanks ShagCA, that reminds me that if you are located in the US, you can also go to the FCC website and get information. They also have an app. Again, that would depend on your location.