restore __pycache__ folder from trash ubuntu 18.04

You don't mention how you intended to restore it,and what led to this error message, so help on the actual question is not possible.

From an other viewpoint, you actually do not need to worry about restoring that folder. __pycache__ is a directory that is automatically created by the Python runtime to store byte-compiled code from the python source in the current folder. Thus, next time you run the code in that folder, python will recompile the code and you will see your __pycache__ folder back.

Note: this behavior is different from older Python versions, where the compiled files were stored in the same directory as the sources.