proposal to create a new wallet. maybe the problem arose because before that I used and updated the portable version and this time installed through the Windows Installer. I used to update an empty wallet. and for the first time decided to update in a hurry non-empty.
Definitely sounds like the "portable" version was used originally.
In that case, you need to look where you had the portable.exe file... in that location you should find the "electrum_data" folder as mentioned by IeSua:
and in that folder you should see "wallets":
Once you find that... you can then either copy the wallet file from there to your "C:\Users\username\AppData\Roaming\Electrum\wallets" folder or you can just use the "File -> Open" option in your installed 3.3.8 version of Electrum to navigate to the wallet file in the portable "electrum_data" folder