does not work "manage.py"

I started learning Django.
Does not create a folder for me “blog”. .\manage.py startapp blog.
If I enter manage.py startapp blog - the system does not recognize the name manage.py

Please tell me what the errors are and how to fix them

Did you check the django tutorial for app creation ? See Writing your first Django app, part 1 | Django documentation | Django

manage.py is not an executable by itself, it’s a python scrit, so you need to execute it using

python manage.py startapp blog

thank you man)

I’m studying django by video, I didn’t know about the documentation