It's been about 7-8 years... from memory, I did not extend the seed...
You must have a copy of the seed phrase of "
default_wallet1" somewhere since it cannot be created without verifying that you've created a backup during wallet creation.
Since it's been a while, you might have just forgotten about it so try to look for it.
BTW, your wallet files aren't backup-up anywhere but your computer since Electrum doesn't have a central server for that.
So, I'd suggest you to stop using that PC at the moment in order to have a good chance of recovering the deleted wallet file through file recovery tools.
Using it further will corrupt the possibly still-recoverable files from the previous installation.