Well, one way is for you to write a program, that it generates many z out of a Gaussian distribution, and then you square those z value into z^2, and plot the distribution of the squared-z. This way, you can visualize it. The graphs below are from this Wikipedia, perhaps you can also try a few different k values and see what you will get?
Feel free to share your graphs, @Hassan_Mohamed6.
If you want to derive the Chi-Square from the Gaussian and have no idea how, then I would google “derive chi-square from gaussian” and see what I find. Make the most of this internet database of most people in this world who had discussed this.
Cheers,
Raymond