Solenoid project, calculation of solenoid specifics

Hi all, i'm trying to calculate solenoid force using this formula: F = (N*I)2 μ0 A / (2 g2)

I can't understand the ralation with A in the formula and also if this formula takes into account the lenght of solenoid.

I explain better:

If i have a solenoid with 2000 turns inner diameter of 10mm wire diameter of 0.1mm and solenoid lenght of 20mm i have 17.66 mH inductance. If i have a solenoid with 2000 turns inner diameter of 10mm wire diameter of 0.1mm and solenoid lenght of 10mm i have 31 mH inductance.

I have more layers of wire in 10mm instead in 20mm and the force is higher.

So, this formula calculate on a single layer? so does not consider the length of solenoid?

I need to calculate on a multiple layer solenoid. There is formula that from Magnetic B-field or Inductance i obtain force on a pice of metal that distant g(stroke)?

How much need to be thick enamelled copper? How i can calculate the thickness necessary? (to not burn solenoid wire)

How i can calculate and ideal solenoid with a force, stroke, time(in ms to fully move plunger) knowed?