Anaconda3におけるJupyter notebookのエラーについて

jupyter notebookにcontentsを表示させたいと思いネット（https://qiita.com/neko-desu/items/3a9ff96e200073e59101）のやり方通りに行ったところjupyter notebookにcontentsも表示できず、起動するたびに以下のようなエラーメッセージが出るようになってしまいました。contentsを表示させてエラーメッセージを出なくするにはどのようにしたら良いですか？

[I 01:25:52.344 NotebookApp] The port 8888 is already in use, trying another port.
[W 01:25:52.349 NotebookApp] Error loading server extension jupyter_nbextensions_configurator
Traceback (most recent call last):
File "C:\Users\tugum\anaconda3\lib\site-packages\notebook\notebookapp.py", line 1942, in init_server_extensions
mod = importlib.import_module(modulename)
File "C:\Users\tugum\anaconda3\lib\importlib_init_.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "", line 1014, in _gcd_import
File "", line 991, in _find_and_load
File "", line 973, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'jupyter_nbextensions_configurator'
[I 01:25:52.747 NotebookApp] JupyterLab extension loaded from C:\Users\tugum\anaconda3\lib\site-packages\jupyterlab
[I 01:25:52.747 NotebookApp] JupyterLab application directory is C:\Users\tugum\anaconda3\share\jupyter\lab
[I 01:25:52.753 NotebookApp] Serving notebooks from local directory: C:\Users\tugum
[I 01:25:52.754 NotebookApp] Jupyter Notebook 6.1.4 is running at:
[I 01:25:52.754 NotebookApp] http://localhost:8889/?token=0861384758ffab616da72aa4a9e8f6c16460662c22e3a72b
[I 01:25:52.754 NotebookApp] or http://127.0.0.1:8889/?token=0861384758ffab616da72aa4a9e8f6c16460662c22e3a72b
[I 01:25:52.754 NotebookApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[C 01:25:52.867 NotebookApp]

To access the notebook, open this file in a browser:
file:///C:/Users/tugum/AppData/Roaming/jupyter/runtime/nbserver-9036-open.html
Or copy and paste one of these URLs:
http://localhost:8889/?token=0861384758ffab616da72aa4a9e8f6c16460662c22e3a72b
or http://127.0.0.1:8889/?token=0861384758ffab616da72aa4a9e8f6c16460662c22e3a72b
[W 01:25:56.086 NotebookApp] 404 GET /nbextensions/nbextensions_configurator/tree_tab/main.js?v=20210502012550 (::1) 61.94ms referer=http://localhost:8889/tree