Web3.js: How to import account if I know address and private key?

[mishell-trickster]

I start ganache-gui and see lot of accounts, they has privat keys and mnemonic phrase. Then I connect to this testnet with nodejs and web3 1.x.x, so my wallet.length is 0. I want to import all wallet from ganache by mnemonic phrase or better import one address using private key. Could I do this? I tried web3.eth.accounts.privateKeyToAccount(privateKey); but its return new account. How it works? Metamask can do this by privateKey.

[mishell-trickster]

I did not know that the key must start with 0x.

[yehan-xiao]

Just post for people might meet the same situation like me...
for web3.eth.accounts.wallet.add(account)
the private key must start with 0x too.

[ankita-p17]

I am using geth 1.9.0 which has web3 version api: "0.20.1",
How can I import account here using key and address?
web3.eth.accounts.wallet.add is returning undefined