Need to find the equation of a curve from a Hand drawing

If your CAD software does not support freeform curves (which I doubt), go for natural cubic splines. https://en.wikipedia.org/wiki/Spline_(mathematics)#Algorithm_for_computing_natural_cubic_splines

You will define the curves from a set of interpolating points. When there are angular points, start a new spline (which they didn't do in the example below).

Note that cubic splines can be converted to cubic Beziers, which are quite commonplace. (You can also try Beziers straight away, but fitting to an existing curve can be more difficult.)

This is the Freedom Tower in $Iran-Tehran$.

And this is how I drew it with 202 equations:

Go to www.desmos.com and paste your picture in the background and try to trace the equation over that. At the beginning it may take some times but it will be easier as you practice more.

And these are the first 58 equations that I wrote, if you need the rest of them I can send them to you: