One more inverse z transform ... a bit more complicated Thank you for all the help teaching me. I am looking at one more inverse z transform and not understanding what to do with it.

$F(t) = m \cdot a(t)$ (i.e. Force = mass $\times$ acceleration)

$F(s) = m \cdot d(s) \cdot s^2 $ (i.e. Where d(s) is displacement and initial position is 0)

Using $s = \frac{1-z^{-1}}T$:

$F(z) = m \cdot d(z) \cdot \frac{1-z^{-1}}{T}^2 $

$F(z) = m \cdot d(z) \cdot \frac{z^{-2} - 2z^{-1} + 1}{T^2} $

I have displacement calculated per sample already from another equation, so I can just substitute that in for $d(z)$. But what on earth do I do with that to get $f[n]$?

Thanks and sorry for all the questions. I unfortunately have zero education on this and it's hard to find simple to understand resources explaining how to do these things.
Okay it's:

$F[n]=m \cdot \frac{d[n−2]−2d[n−1]+d[n]}{T^2}$