How to get correct Private key from BitPay testnet wallet

I’m using BitPay testnet wallet on mac and. I have exported the private key as a json file and then I copied all of it’s content paste in this tool to get WIF key and when I put the xPrivKey into my key.txt file which is mentioned in conf.ini I got another error as:

pycoin.encoding.EncodingError: unexpected first byte of WIF xprv9s21ZrQH143K31uJMPo9x8bWpuj9HS6cSAkJ67CDyzcB5LKwLMswKJECJz8LgpiAwzWjjY6p1943A9GYA12J2uPgBsXgqYHTqLS72e1pimr

Tried getting rid of all the surrounding characters in the json file and leave only the private key?
For example if your export looks like {'key': '123qwe123'} isntead of entering all that in the key file just leave 123qwe123
maybe that helps?

I’m using BitPay app on mac for my bitcoin testnet wallet. When I export the wallet (privateKey) here’s what I got:

{“iv”:“G3kyjq8Q70SkUMRqIT/55Q==”,“v”:1,“iter”:10000,“ks”:128,“ts”:64,“mode”:“ccm”,“adata”:"",“cipher”:“aes”,“salt”:“JLUnNJ/Cqj8=”,“ct”:“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”}

I don’t know what should I pass as the key. I tried to get the private key from this JSON by using this tool and the Key I mentioned above in the question is generated through this tool.