What do I need at an order to show cause re dismissal hearing and who requests this hearing the court or the landlord who I was granted the motion to vacate judgment against?

It depends on who filed the order and what the subject is about.

Usually a show cause hearing requires a good argument to support or deny what the hearing is about. You may need evidence and testimony to help support that argument however. And what that is depends on what you have or can get on the issue.

But generally a show cause hearing is where you or your opponent must show a good enough reason to the court so they can make a decision. Best way to think of it is to keep this in mind "Show Cause Why this court ..." the issue can be anything connected to the case and/or decisions made by the court. There are rules that govern this but it is far too complicated to go into here.