You need to use mpy-cross, which you can either build from source (make sure you checkout at the same version tag as your firmware), or the much easier option is to install using pip (see https://pypi.org/project/mpy-cross/ )
Use mpy-cross on the PC to compile you .py files into .mpy files. I have a few compiled versions here: https://github.com/robert-hh/Shared-Stuff. Other people share that too. A search on the board will reveal it.