Using C++ code in flutter problem

Hi.

I have a question for using with c++.

I have work with below link.

But. meet the problem in first step.
typing ‘flutter create --platforms=android,ios --template=plugin native_add’ in termanal.
Okay i successed.
After open the folder in VScode, I met the error as below image.

This is made automatically not typing own.
My PC has mingW installed so i can build c++ with VSCode.

Could you tell me in detail how to solve this problem if had solved?

Thx.