How do you script minecraft clouds to spawn and glide across the sky before disparaging? [closed]

I am making a similar game to minecraft in roblox, i'm calling in Bloxcraft. I wanted to make 3d clouds pass by in the sky, these clouds would have random sizes and would spawn in randomly they would pass across high above the base plate. after leaving the base plate air space the cloud would despawn. these clouds would be simple white blocks, like the ones you see in minecraft, and at random they will stop spawning, and change to a grey color to form one big cloud. To make it look like it is stormy. once its done that i can add a rain script, then once the rain stops it the cloud script would start again.

I hope you can make any sense of this. I tried to explain like you have never played minecraft before. I want to know how to do something like this https://www.youtube.com/watch?v=2s3AxUj0ivc