How to convert any native app to ionic cordova plugin

Ionic Native
1

Hi,
my question is
How i can include any native functionality like


in my ionic v4 app?
how to convert any native app to ionic cordova plugin
2

How is this thing different from any of the myriad existing barcode scanners?

3

It’s not about barcode scanners,
I do need to know how i can convert any Android app to ionic cordova plugin.

so that i can use that native functionality as i want to have that in my ionic app.