The most reliable way to get EVE-NG Pro is through the official website. The license is generally sold as a yearly subscription. Create an account on the official EVE-NG site. Purchase: Select the Professional Edition license.
Scripts that claim to set up a "cracked" version of the environment automatically. The Risks of Using Unofficial Licenses eve-ng pro license key github
If the cost of EVE-NG Pro is a barrier, there are other legal ways to build high-level labs: The most reliable way to get EVE-NG Pro