There is no blockchain balance. Blockchain is a technology system, not related to economy. Bitcoin is a payment made to promote blockchain technology. You can convert
Bitcoin to cash on exchange through the exchange, you can find a seller from a country you are on
https://localbitcoins.com.
Im also saying the same thing, if you want to withdraw your Bitcoin you should make use of localbitcoins to find an exchanger and then sell to them. But I think the op knows it is called Bitcoin, cause from what he said how do I withdraw my blockchain balance, so theres no need to think hes a dummy.