Wipe board + leaving the battlefield effect : how to resolve ?

Hello,

As I'm still learning mtg I came accross a situation in mtg Arena in which I didn't understood at all how the effect resolved :

Let's say that I have [[Undead Augur]] + [[Headless Rider]] + 3 other zombies without particular effect. I cast a Damnation on my turn, how does my Undead Augur and Headless Rider effects will play ? Do I choose the order ? How many 2/2 token are coming in play and how many cards will I draw ?

If you want to provide and explain even more complex cases I'm always eager to learn :)

Thank you !