Get data from VSTS

VSTS Task Definition, i.e. EffortWhat data can I import from VSTS ?  We use EPIC, USE CASE, TASK, etc. very extensively in our Software Engineering, how can I find out what data i can import into Power BI Desktop?  For example when looking at a TASK in VSTS there are Effort values, Orignal Estimate, Remaining, and Completed.  Where can this information be found please?