The definition of force is given by the secon Law of Newton: Force = mass * acceleration.
So, the basic components of the formula for finding force are mass and acceleration. That is, if you know the mass of an object and the acceleration of it, you can find the external force (the net external force) that is acting over the object.
There are other formulas for finding force for special systems. For example, for springs, you use the law of Hook: Force = - k *x^2. Where k is the elastic constant of the spring and x is the displacement from the equilibrium point.
So, depending on the contex you could need different formulas. Without more contex I'd say you are talking about the second law of Newton: Force = mass * acceleration.