Trying to create my first pet name generator

Respected users,
Myself is teddy i was trying to create name generator in python using openAI. But when i run these in terminal to run the app.
python -m venv venv
. venv/bin/activate
pip install -r requirements.txt
flask run

its shows:
Command ‘python’ not found, did you mean:
command ‘python3’ from deb python3
command ‘python’ from deb python-is-python3[
bash: venv/bin/activate: No such file or directory

then i clicked: http://localhost:5000/

but page is not working. Can you help ? i am attaching screenshot.