What do you call the document containing all of the details of a military mission? I know the "mission briefing" expose the details of the mission, but what do you call the document and not the event where the details of the mission is being put forth?
It is called an operations order. It is abbreviated as OPORD. It has five paragraphs:
"S" Situation, "M" Mission, "E" Execution, "A" Administration/Logistics, "C" Command/Signal
Interestingly, in the context of preparing for war, it is called a war plan, as Jason Bassford has said. Operations orders do vary by country, but there are several which follow the U.S. model very closely.
The manual that deals with OPORDs in detail is FM 5-0: The Operations Process.
From Wikipedia, there is military operation plan:
A military operation plan (also called a war plan before World War II) is a formal plan for military armed forces, their military organizations and units to conduct operations, as drawn up by commanders within the combat operations process in achieving objectives before or during a conflict. Military plans are generally produced in accordance with the military doctrine of the troops involved.
I suspect, however, that different countries and different branches of the military will have different specific terminology.