[AussieKenDoll]

I plotted the Job's plot to find out the Stoichiometry of Fe(III)-Salicylic acid complex and the stoichiometry is 3 which is correct, now I have to find the Stability constant of the Fe(III)-Salicylic acid complex, How do I find the concentrations for the stability constant?
Fe(III)solution concentration is 0.01 M
Salicylic acid concentration is 0.01M

Using Beer-Lambert law A=εCl 
0.019 = 0.01(εl)
(εl)=1.9
Stability constant = (0.547*1.9)/(0.008*0.019)=6837.5
Is this correct?

***See the attached table

[mjc123]

This doesn't look like a good Job plot. It's too flat across the middle. I suspect your absorbance is saturating. It is usually recommended to stay within the range A ≤ 0.1 to get good Beer-Lambert linearity of response. Can you repeat the experiment with lower concentrations (or shorter path length, e.g. if you are using a 1 cm cell, try a 1 mm cell)?

[AussieKenDoll]

I already did the experiment and those are the values I got.
I plot the job's plot and got correctly stoichiometric ratio as 3 now i have to find the Stability constant? How do I find it?

[mjc123]

You can't get it from bad data. In any case, I think you need a value for the extinction coefficient of the complex in order to calculate the concentration.

Stability constant = (0.547*1.9)/(0.008*0.019)=6837.5

Where did you get those numbers, and what formula are you using for stability constant?
How did you get the stoichiometry 3? It looks difficult to get any number with confidence out of this curve. But see e.g. https://www.odinity.com/determination-salicylate-via-reaction-feiii/