[need help] how to find "upgradeCode" from(in) a exsit app(build with electron-winstaller)

[Stormpass]

upgradeCode (string, optional) - A unique UUID used by your app to identify itself. This module will generate one for you, but it is important to reuse it to enable conflict-free upgrades.

I have previously packaged an app using squirrel.windows and have a few users who have installed and used it.
Now I want to switch to wix packaging

How can I set this "upgradeCode" to allow users to overwrite the previous app directly instead of installing a new one.
Can anyone help me with this? Thanks for your help!