The path to eM Client.exe in Windows is:-
C:\Program Files (x86)\eM Client\MailClient.exe
If you are wanting the path location to create eg: desktop or taskbar shortcuts to directly open the various sections of eM Client such as mail, calendar, contacts etc, see the below post in the following thread from @lilles which shows specific parameters to do that.
https://forum.emclient.com/t/shortcut-to-open-em-calendar/55827/7