[FluidKo]

Hello everybody~!
I want plot residual.
So I've followd below video.
https://www.youtube.com/watch?v=q0q_qwprEL4&t=278s
But I get a error message like below

Traceback (most recent call last):
  File "/usr/lib/command-not-found", line 28, in <module>
    from CommandNotFound import CommandNotFound
  File "/usr/lib/python3/dist-packages/CommandNotFound/CommandNotFound.py", line 19, in <module>
    from CommandNotFound.db.db import SqliteDatabase
  File "/usr/lib/python3/dist-packages/CommandNotFound/db/db.py", line 5, in <module>
    import apt_pkg
ImportError: /opt/OpenFOAM/OpenFOAM-v2012/ThirdParty/platforms/linux64/gcc-6.3.0/lib64/libstdc++.so.6: version `GLIBCXX_3.4.26' not found (required 
by /lib/x86_64-linux-gnu/libapt-pkg.so.6.0)

What is the problem?
I have no idea about coding, Linux and Ubuntu. I've never done those things before.
Would you tell me simple way to solve this problem?
Thank you~!