For any wallet you had in the tools menu "export private key" or something.
It used to export into a file. Usually asks for password, but this time you need it unprotected.
I hope it's close to that in your wallet too.
Edit: I found this for Multibit HD http://bitcoin.stackexchange.com/questions/40507/how-can-you-extract-private-keys-from-multibit-hd
Why do you want to export your private keys? If you use "Repair Wallet"[1] it should remove unconfirmed transactions[2]. If it does not, you can restore the wallet from your seed words. Once you have done that, you can create a double spend that pays a higher fee and sends the coins to yourself instead of the other party.
[1] https://multibit.org/help/hd0.3/repair-wallet.html
[2] Im not entirely sure here, but thats what "reset" used to do on classic.