Financial modeling of public companies

How do you model public firms given they provide so little information about their operations? They publish almost no information about units sold, product price, headcount, etc. Apple doesn’t even publish the number of iPhones sold. How is one supposed to make a financial model for a public company? Where do I get this data? In IB and PE, you get access to pretty much any information you ask the company, so making a model is fairly simple.