There are two places, where you can find these unwanted Windows 10 Start Menu folder and icons.

To delete theme manually, press Win + R and paste the following code one by one in the Run box and delete theme.

%ProgramData%\Microsoft\Windows\Start Menu\Programs

%AppData%\Microsoft\Windows\Start Menu\Programs

You can open theme from Windows Explorer too, if you don’t like to use Run box.

C:\ProgramData\Microsoft\Windows\Start Menu\Programs
C:\Users\yourUserName\AppData\Roaming\Microsoft\Windows\Start Menu\Programs

Replace the user name in the second explorer location.