Currently there are limited options for executing Python3 code in Splunk. The simpler solutions call for using a wrapper script which will execute using the Splunk built-in Python interpreter and then call a different script using another interpreter in some way.
A more complicated option but with greater flexibility and options is an app called PyDen. This app allows you to install additional versions of CPython, create virtual environments, and install PyPI packages to the environments.
I also have to point out that ipynb files are Jupyter notebooks and would need to be converted to standard .py files first.