My advice is to ask for your money back. If what you have told us is
correct, this developer doesn’t sound even a little bit competent to me
and I would have no confidence that the program will work correctly. But
maybe I am wrong.
If you are using Python 3.9, there will not be a “python37” folder,
because you are using Python 3.9 not 3.7.
If he is the developer of the program, I don’t know why he didn’t
contact us to ask for help. He would be able to answer questions about
what he tried and what results he got better than you can.
How did this developer try to install Python? What happened when he
tried it? Did he get any error messages? What were they?
What OS are you using? Linux, Mac, Windows, something else?
On Windows, you can get it from the Microsoft App Store, for free. It
will install the Python interpreter and all the standard modules.
If you are using a Mac, I’m afraid that I can’t help you. I know very
little about modern Macs, the last time I used one was Mac OS 7 more
than twenty years ago.
On Linux, it will depend on your distro (Ubunto, Debian, Fedora,
something else?). Tell us what your distro is, and the version, and we
can probably tell you what to do.