Hi.
An array is just a means of storing information, you can use a dictionary, a text file, or even just variables.
This is a very broad question and in addition to storing information, you need to check the conditions of execution, if it is collecting or killing a mob, then you also need to record how much you collect and destroy in a variable and then compare.
This is a full-fledged mechanic and looks like an iceberg, where there are much more actions under the hood than on the outside. I can't just write this to you, but I can give you an example.
I created it a long time ago, and it had quests, so you might find it useful.
File *.c3p