i want to purchase the bitcoin based ad network script from where i can get the script of ad network
Code for ad networks are usually held pretty close to the chest, let alone ones that are bitcoin-based. You're likely going to need to hire a developer to do this, and it will easily cost you $10,000 - $50,000 USD.
You need to find professional developers for hire that also know how to code with bitcoin, I would suggest trying on other sites.