How to predict the revenue of a private company using their public information?

Assess the extent of revenue and accounting cash flow 

If your have also history for revenue you can implement your potintioal revenue according your exppert also.

You kind of have to look at all of the above.
Knowing how many employees, the type of employees, the industry, services/product provided, current customers, etc give you as close of a guess as your going to get.
At best you can geusstimate the potential revenue of a company but it's impossible to come up with a completely accurate number.

preparing cash flow statement using the information of balance sheets and income statemnets