If it's a multibit seed then you need to set the correct "Derivation Path" in electrum.

If yes proceed as follows:

1. Electrum Creat/Restore
2. I allready have a seed
3. Enter your Seed, Click Option, BIP39 Seed, Click Next
4. Change Derivation Path from  ( m/44'/0'/0')  to ( m/0' ) Click Next
5. Set Password and Restore Wallet

Edit/ Ok, I've just seen that it's probably an old Electrum seed so my guide will not work.