OP, be careful with PM (Personal Message) that claim they can help you since usually it's scam attempt.
Legacy wallets are just collections of random key pairs and don't follow a descriptor-based derivation. So there is no master private key for these.
They might definitely be legacy wallets. I think I created them back in 2013 or close to that.
Looking at
https://bitcoincore.org/en/2016/08/23/release-0.13.0/, HD wallet support exist since 2016.
So that means that there is no easy way to import them into Electrum?
Create a new wallet, choose "Import Bitcoin addresses or private keys", and import the addresses. You'll create a watch-only wallet that shows your balance.
Note and disclaimer: if you happen to have mined or received "to pubkey", it will NOT show up this way!
Also note that if there are too many TX with those address, Electrum may take some time to get all data, feels laggy misbehave.