However, how would you know how many total btc addresses you have BTC in? For example someone could have 1 btc and that 1 btc could be in 30 different btc addresses on their nano ledger s plus?
You can import the master public key on Electrum.
To do that, click on standard wallet-> use a master key -> paste your master public key -> set your password.
To see the addresses that are funded. Click on 'view' on the GUI -> check (✔️) coins. Coins will appear on the GUI, click on coins and you will see your funded addresses.
You can also use other coin control wallet like Sparrow and Bluewallet for it.
Do not import your seed phrase or master private key. Import your master public key which will start from xpub, ypub or zpub. It is a watch-only wallet and you will not be able to use the wallet to spend your coins.