1 Billion are the US counting measures, whereas 1 Core are Indian counting measures. If we want to know the relation between the two counting measures then we can first establish a connection between the currency of the two nations, i.e. Dollar for US and Rupee for India.
How to calculate Dollars into rupees:
In India, we use "lakh" and "crore" to talk about big numbers after a thousand. But in the US, they use "million" and "billion" after a thousand.

In India, 1 crore is equal to 100 lakhs, and hence,
1 crore = 1,00,00,000
1 billion is the same as 1000 million, so they are equal.
1 billion = 1,000,000,000
So, when we look at both counting systems, we find that 1 billion is the same as 100 crore in the Indian system.
Hence,
1 USD = 80 INR. (USD: US Dollars and INR: Indian Rupees)
1 billion USD in Rupees = 80 billion INR = 8000 crore INR.
