The code isn't complete. Is it a 3D matrix? If so, have you considered using Image3D?

If not, please include a simple example of the kind of data you are trying to visualize.

Please see the documentation for ListPlot3D:

https://reference.wolfram.com/language/ref/ListPlot3D.html

Is this what you want? What about ListPointPlot?

https://reference.wolfram.com/language/ref/ListPointPlot3D.html

Without an example, I can only really guess at what you are talking about. If these don't work, please include:

1. A simple example of the kind of input you want.
2. A sketch of the kind of output you want.

When asking a new question, it is best to ask it in a new post. This allows other people who might be able to help you to see the new question.

You should not use NonlinearModelFit to estimate the parameters of a Multidimensional Gaussian distribution. You should use EstimateDistribution or something similar.

Once you've estimated the distribution you can create a 3D plot using something like:

Plot3D[PDF[MultinormalDistribution[....], x], ..........]

And you can combine plots together using the Show command.

BTW, I can't guess what your data looks like, but I'm guessing you should use the raw data with Histogram3D instead of a point plot.