You should be able to run nbconvert utility from any python environment, just need to pip install it. I don’t think it requires jupyter, you should be able to use it directly - see API description here.
Slicer’s JupyterNotebooksLib has a convenience function for getting the full path of your notebook:
import JupyterNotebooksLib as slicernb
notebook_path = slicernb.notebookPath()