power spectral density plot

Hello,

I need help in my code, i want to plot a subplot of power spectral density with my frequency ranging from 0 to 35. I am using data extracted from a plot. I want my PSD to be from the ydata (vertical acceleration of signal) with respect to the xdata (time) of the extracted data. with ylabel (PSD of vertical acceleration (m^2/s^4/Hz)) and xlabel (f(Hz)). i want my sampling frequency to be 1000Hz. Also i want my graph to have two x-axes with the one on the top position having the values from this (f/S/L); f being my frequency, S is speed and L length. I have tried to solve it with my code that i have attached below but i have not been successful with placing the top position x-axis range as i wanted and also the frequency range in the lower x-axis is not as desired.

Here in, i have attached the graph from which i have extracted the data, and the code i have used.

your help will be highly appreciated. Thank you,