You shouldn't need to do anything special to upgrade to a new Portable version. Electrum reads the wallets/configurations/etc from your User directory folder.
For example, on recent versions of Windows, it stores the data in the following folder
Users/YourUserName/AppData/Roaming/Electrum
and for Mac/Linux it will be in
Just download the new version and you shouldn't have an issue.
Portable versions has a different behavior as compared to executable and installer. Portable versions are configured to search for the data directory within the folder the portable version is in. This is what differentiating itself from other versions.
If you opened the client in F:\, the wallet directory will be F:\electrum_data.