How can I create a chest with a custom lot in version 2021.1?

Hello everyone, I recently wanted to create a mod with a structure that has chest with random loots I watched a video of it on version 2020.1 and from what I understand it only works on Minecraft 1.14 How can I make random lotos in chest in the new version of MCreator?

Please reply me quickly it is very urgent!
Here is a link to a video I saw: https://www.youtube.com/watch?v=aDAhhLADH_M