Jupyter cannot display pictures and formulas and run code with markdown files

I downloaded the latest Notebooks from GitHub. It is in markdown format, but I don’t know how to make it display pictures, formulas and run code on jupyter, just like the previous .Ipynb format.

I tried to install different versions of miniconda and anaconda, or install the notedown plug-in, but it didn’t help. could you help me? Thanks in advance!