AFAIK invalid syntax means there is no command registered with "run_electrum" by phyton3. It means python can't find any program/file/command named "run_electrum" from your working directory, installed module or path variable. I don't think this is dependency issues.

Update: The problem is missing dependencies, update your phyton.

Where did you try to run the command? From the desktop?
Try to run the command from the Electrum files folder that you've downloaded. Download the latest electrum package, it contains a file named "run_electrum". This is what executed by that command.

You can simply use this command to run Electrum from the root directory: