Problem with VSCODE and PYTHON to run basic program

Hi. I am taking the python for developers course. I am working in Windows 10 professional. I downloaded python 3.9.4 and VSCODE. I got stuck in the 3rd module (Code editors), because when I run the command “HelloWorld $python app.py”, I get the error message below. I tried reinstalling python and even adding the python extension in vscode, and no difference.

The command is python app.py . “HelloWorld” and “$” are part of the prompt.

OMG!. That was it! thank you so much.