In latest version of Electrum (v3.0.2)... Right click on the address tab ("View - Show Addresses" if you can't see the Addresses tab)... select "Details"

You'll see the address, public keys... and the "redeem script"... Copy/Paste that Redeem script into coinb.in "verify": https://coinb.in/#verify

It will decode it and show you the addresses that match the public keys.... you will then need to use the original wallets to get the private keys for the addresses.