I am trying to create an equation for the stopping distance with respect to the force applied to the braking pads.
You can use the work energy theorem which states that the net work done on an object equals its change in kinetic energy, or
$$W_{net}=\frac{mv_{f}^2}{2}-\frac{mv_{i}^2}{2}$$
where $f$ and $i$ indicate final and initial velocities.
The net work equals the average net force times the stopping distance. Since the final velocity is zero, we have
$$F_{net}d=-\frac{mv_{i}^2}{2}$$
Where $F_{net}$ is the average braking force and $d$ is the stopping distance.
The work is negative because the direction of the stopping force is opposite the displacement of the vehicle. Negative work means energy is removed from the car. In this case the brakes remove kinetic energy from the car doing friction work and dissipating the energy as heat.
Hope this helps.