Bitcoin-Qt client wallet.dat extract private key to import on another service

I have a file: wallet.dat where should be saved one or more private keys of my old wallet linked to one/more public btc addresses. I also had more than a wallet, so I don't really know if there are some created address with an amount of money in that file or not. Of course, I don't want to download 500 gbs of transactions since 2009 using Qt-Coin and my idea was to extract private keys in order to import them on another wallet like blockchain.com. I managed to use some open source tool (wt_extract_keys.py https://github.com/akx/walletool) to extract private keys, one seemed to work but the format of private keys seems to be not compatible because blockchain.com requires a private key in a wif format and what I got is a very big private non-compressed key. So how can I get the private key/s with the right format this if it's possible? What do you suggest?