Hi. Just starting to learn this program. Was wondering how I retrieve an object from, let's say a rat, but only after you kill it. Eg: you kill the rat, then you can get rat meat from it?

You could just remove the rat npc and then insert an object which is "rat meat". So when dead, it converts.

If not that, then you'd have to figure out the player experience first, and then you can work out the how. For instance, the rat would become a dead rat, but how does the player know they can get rat meat from the dead rat? What would the command be (e.g. take meat from rat) or do they now see "a dead rat (containing rat meat)" and they can just take the rat meat? If you can work out the design, how you want it to work, then someone should be able to guide you to how to make it happen.

Hey. Thanks for your help. I've figured it out

Disregard this if you've already accomplished it, but the way I would handle the situation would be:
when the player kills the rat, move the 'rat' object to an unaccessable room (eg ITEM ROOM for all purpose storage)
then swap in an item called 'dead rat'
which is a container with visible children.
so it would work out like:
kill rat. You kill the rat.
>look
you can see a dead rat (containing: rat meat, whiskers)
or something along those lines.