What Math Courses are required for pursuing Economics Phd in US?
To answer the general question of how to find graduate admissions required or recommended coursework, you can typically visit target program admissions pages. 

If there are official requirements, they will be listed in the prospective applicants section, providing you course types and expected credits/periods of knowledge. If they are recommendations, this gives you a guideline for what you should aim to complete.

For example, UMD asks for:


  In general, our admitted students have GPA's well above a "B" average, particularly in economics and mathematics; very high GRE's (particularly quantitative); math preparation that includes at a minimum three semesters of calculus, a semester of linear algebra, and a semester of differential equations;


I would assume that alternative similar classes, or classes above this level, are also accepted (verify with admissions department, as always).

If this list is not available online or you need help, calling the admissions department is a great way to get info as well. You can provide your list of current and potential mathematics courses and see if you're missing anything.