Webpacker::Manifest::MissingEntryError in Pioneers#index Error on Rails

Good evening
I need your help please, Im a newbie at web applications and i am taking a course and i was struggling the web server to get to work
this is when the webeserver is up:

ubuntu@ubuntu-N53SV:~/hello_WWW$ rails server
=> Booting Puma
=> Rails 6.0.0 application starting in development 
=> Run `rails server --help` for more startup options
Puma starting in single mode...
* Version 3.12.1 (ruby 2.6.3-p62), codename: Llamas in Pajamas
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://localhost:3000

because rails use sql lite i typed the below commands to create a table and a schema:

rails generate scaffold pioneer first_name:string last_name:string
   rake db:migrate

everything was ok so far until i opened the browser and typed: http://localhost:3000/pionners it yield a lot of errors_

ActionView::Template::Error (Webpacker can't find application in /home/ubuntu/hello_WWW/public/packs/manifest.json. Possible causes:
1. You want to set webpacker.yml value of compile to true for your environment
   unless you are using the `webpack -w` or the webpack-dev-server.
2. webpack has not yet re-run to reflect updates.
3. You have misconfigured Webpacker's config/webpacker.yml file.
4. Your webpack configuration is not creating a manifest.
Your manifest contains:
{
}
):
     6:     <%= csp_meta_tag %>
     7: 
     8:     <%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
     9:     <%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %>
    10:   </head>
    11: 
    12:   <body>
  
app/views/layouts/application.html.erb:9

In the Root directory of the application i searched all elements contain the word pioneer so :

ubuntu@ubuntu-N53SV:~/hello_WWW$ find ./ -name *pione*
./app/assets/stylesheets/pioneers.scss
./app/assets/stylesheets/pioners.scss
./app/views/pioneers
./app/views/pioneers/_pioneer.json.jbuilder
./app/views/pioners
./app/views/pioners/_pioner.json.jbuilder
./app/helpers/pioneers_helper.rb
./app/helpers/pioners_helper.rb
./app/models/pioner.rb
./app/models/pioneer.rb
./app/controllers/pioneers_controller.rb
./app/controllers/pioners_controller.rb
./db/migrate/20191201015729_create_pioneers.rb
./test/system/pioneers_test.rb
./test/system/pioners_test.rb
./test/fixtures/pioneers.yml
./test/fixtures/pioners.yml
./test/models/pioneer_test.rb
./test/models/pioner_test.rb
./test/controllers/pioners_controller_test.rb
./test/controllers/pioneers_controller_test.rb

Could you explain me what this error is about? or what did i do wrong? or give me a shed light all what this is about.
As i told you this is the first time i experiment it and whenever errors came up i dont know how to deal with or how to put out that fire

Thanks for your help in advanced

You need to correctly set up webpacker first.

From your error message:

ActionView::Template::Error (Webpacker can't find application in /home/ubuntu/hello_WWW/public/packs/manifest.json. Possible causes:
1. You want to set webpacker.yml value of compile to true for your environment
   unless you are using the `webpack -w` or the webpack-dev-server.
2. webpack has not yet re-run to reflect updates.
3. You have misconfigured Webpacker's config/webpacker.yml file.
4. Your webpack configuration is not creating a manifest.

Until you resolve your webpacker configuration, you will continue to have issues.

If you use NPM (Node Package Manager), this will be easier for you, I think.

could you provide an useful link to display the instructions how to install and set up correctly my webpacker?

Thanks you very much for your support

As mentioned, I think best to set up NPM first and use NPM to manage Webpacker and other JS apps.