Check How install Tryton in Windows 10? (Regular and Anaconda) - #7 by edbo . In short, Windows doesn’t recognize the commands, you have to use the path where the command is and use python before to make sure Python is used to execute the file.
If you have Tryton server installed in a virtual environment you will find it as described in the link. If you have Tryton server installed globally, it will be in the site-packages directory of your Python installation. No idea where it actually is, so do a search for trytond-admin.