Is it true or false a postulate is a statement that needs to be proven?

No. A postulate is a nound and is:-

• something stated that is taken as self-evident or assumed as the basis of an argument
• a necessary condition or prerequisite in an argument
• a fundamental principle that is understood
• an unproved and indemonstrable statement that should be taken for granted: used as aninitial premise or underlying hypothesis in a process of reasoning