How to convert .angular-cli.json to angular.json (Angular 6 Migration)

Error: Local workspace file ('angular.json') could not be found.

Well, after running the following commands for migrating an angular app 5 to angular 6, I realized that the angular-cli.json hadn't been converted as you can see in the screenshot bellow:

npm install -g @angular/cli
npm install @angular/cli
ng update @angular/cli
ng update @angular/core
ng update @angular/material (I didn't execute this because I am not using Angular Material)

So, executing this command, I fixed this error:

ng update @angular/cli --from=1.7.4 --migrate-only

That's it! Now, you can go ahead with *ng serve*
Happy Coding!