So I transferred over the coins to another wallet, and then I used the dumpprivkey command in debug of BitcoinCore to get my private key. The only problem now is almost every Private key that I try to sweep into Coinimi wallet comes back with the message " the private key does not contain any funds". I've had more or less the same amount of BTC in my wallet since Mt.Gox exchange flopped, but all Coinimi could sweep out was a .1 BCH. How is that?
I use Bitcoin Core long time ago, but what you really need is to get all your private keys from receive/change addresses. I found that this was possible back in 2016, but I am not sure will it work with version of Core you using today.
the command is dumpwallet you can use it from the terminal and you must give it a full path, e.g.
dumpwallet c:\mykeys.txt
If you have set a password you need to unlock the wallet first. The below command will unlock it for 60 seconds.
walletpassphrase PASSWORD 60
They will be exported unencrypted(!) so be careful.
Only thing you need to change is 60 to 600, so wallet will stay unlock for 600 seconds. Also there will be problem probably with a large number of addresses you will get, but solution for that is to filter them to only
change and
label, which means only those address which contain some balance.
For more info visit :
How to dump all private keys