There's no single GPA cutoff for Cum Laude in graduate school. The requirements vary significantly between universities and even between departments within the same university. Some institutions may not even use the Latin honors system (Cum Laude, Magna Cum Laude, Summa Cum Laude) for graduate degrees at all.
To find the GPA requirement, you need to check the specific guidelines of the graduate program at the university you're interested in. Look for information on their website, usually within the graduate admissions or academic regulations section.