Generate new wallets.

Hello there, i didn't find an example to generate new wallets so i wanted to ask if using the bip39 lib and use `const mnemonic = bip39.generateMnemonic()` can actually generate a new wallet?
And if you allow me to ask, How can I verify the memotecnic wallet created is not an existing one? . If you have reference where I can find this info, I will appriciate it. Thanks!