What is the equation for initial velocity?

Initial velocity is 3.5. The equation is s = ut + 1/2at^2, where s - distance, u - inititial velocity, and a - acceleration. How do I modify the acceleration formula to one that gives me initial velocity? You can't change the acceleration formula to one that gives you the initial velocity you want, as a=v/t.

The equation for initial velocity is s = ut + 1/2at^2, where s = distance, u = initial velocity, and a = acceleration.