how upgrade angular cli 6 to angular cli 8

Question

i have the version 6.2.3 of angular cli, and for the node js i have the vesion 12.6.0

Angular CLI: 6.2.3
Node: 12.6.0
OS: win32 x64
Angular:
...

Package                      Version
------------------------------------------------------
@angular-devkit/architect    <error>
@angular-devkit/core         <error>
@angular-devkit/schematics   <error>
@schematics/angular          <error>
@schematics/update           <error>
rxjs                         <error>

i want to upgrade to angular 8, i followed the below command, but it stayed the some version

npm uninstall -g angular-cli

npm cache verify

npm cache clean

npm install -g @angular/cli@latest

Possible duplicate of How to upgrade Angular CLI to the latest version — Juanes30
To update the versions of Angular you're using, check out the Angular Update Guide for more info. — Edric