Backing up an Electrum wallet
There are 3 approaches to backup/restore your Electrum wallet with Bitcoin, depending on whether you use Electrum to manage a HD or non-HD wallet, you may or may not have a 'seed'.

If your wallet is a HD wallet, to restore/backup your wallet, simply use the 'seed' (12 words).

If your wallet is not HD, to restore/backup your wallet, simply restore/backup your wallet via private keys.

If you don't know/care whether your wallet is HD or not, simply backup (save a copy of) the whole Electrum wallet's data file to you USB drive and move it to another computer. You can use Electrum on other computers to open the data file.

I wrote this 3 Approaches to Backup Electrum for your reference with some screenshots in more details. Hope it helps.