Answers for "how to chnage the version of python your are using in cmd"

how to change pythoin version

conda install python=3.6

python update cmd

First install chocolatey:
$ @"%SystemRoot%System32WindowsPowerShellv1.0powershell.exe" -NoProfile -InputFormat None -ExecutionPolicy Bypass -Command "[System.Net.ServicePointManager]::SecurityProtocol = 3072; iex ((New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1'))" && SET "PATH=%PATH%;%ALLUSERSPROFILE%chocolateybin"
#here is the documentation about chocolatey: https://chocolatey.org/docs/why
#exit or refresh cmd, then run
$ choco upgrade python -y