How would I replace all spaces with dashes in a string?

So I have this basic string script that I'm using for a plugin:

local string = "Hello World"
print(string)

The problem is I cant figure out how I could make it so that it detects spaces in the string and replaces them with dashes, like a url. Example: Hello World --> Hello-World. Also, is it possible to have a button that copies the string to the player's clipboard?