Npx @capacitor/cli plugin:generate command displaying error?

I am trying to create a new plugin in capaciter for all of this

A plugin for Android , iOS , Web & PWA (all 4) to do this ::

Grant file storage access
Choose only Video File via file browser (single and multi)
Display Video in Video Player
Upload File as binary upload to Backblaze endpoint

So I tried to create a plugin with following command

mkdir myplugin && cd myplugin

npx @capacitor/cli plugin:generate

Now the npx @capacitor/cli plugin:generate command displaying error

Cannot open assembly ‘plugin:generate’: No such file or directory.

Why this error occuring ? pls help me?