Filter data by using dependent combo boxes

Hi. I have seen a post similar to my query which I have found here.

But because I hardly understand the codes brought up in there, I couldn't make adjustments to suit my data.

I have attatched a sample file I've made by referring to @gsrai31's post. What I would like is that (i) filtered data will only be displayed only after the user has made selections from the three dependent combo boxes (i. e. the second drop down list depends on the choice the user has made from the first, and so on) and (ii) to understand the procedures/lines of the VBA code so I could make necessary adjustments for it is certain that I will encounter other datasets that would require similar excel function.