13 word seed phrases where the standard for Electrum 2.0 - 2.6.4:
https://bitcoinelectrum.com/frequently-asked-questions/#why-wont-electrum-accept-my-seed-when-i-attempt-to-restore-my-wallet-from-itThey switched to 12 word seed phrases with 2.7.0.
You should be able to restore your wallet with the 13 seed words by downloading one of the older Electrum versions from the official archives:
https://download.electrum.org/2.6.4 should do the job:
https://download.electrum.org/2.6.4/Once you've successfully recovered your old wallet you'll want to send your coins to a new wallet, generated using the latest version of Electrum, as there are some known issues / exploits with the older versions. Don't forget to backup the seed words of the new wallet (should be 12 words) before sending your coins there!
Assuming you haven't moved those coins since before the Bitcoin hard forks (August 2017) you'll also have some forked coins to claim. There are plenty of threads that should help with that, but if anything be extra careful with fork wallets because there have been many cases of malware surrounding those (ie. clear out your Bitcoins before trying to claim fork coins and don't install any fork coin wallets on your main PC -- use a VM or an old laptop that you aren't using anymore).