How do I get a reference to command buffer

[lethal granite]

There's only old guides of accessing command buffers, such as this:
https://www.youtube.com/watch?v=hALEF5f7Mos
They use World.GetOrCreateSystem<EndSimulationEntityCommandBufferSystem>(), which does not work with ISystem, and no longer works with SystemBase. Where can I find updated guide?
I'm trying to add destruction of entities to a buffer