RE: Check criteria of Management Reporter reports
                     
                    
                      
                        That is likely what I'd do too... 
However, you have to keep in mind that if your MR 2012 is configured to use the DataMart connector instead of the Legacy connector, it's not going to hit the GP company DB's, but the DM DB.. .in which case the whole query will be useless as the table structure is very confusing in the MR DM DB.
You could install the Legacy connector temporarily and see how the trace results look like.. 
However, I'm questioning all the efforts of getting down to this, since PowerBI isn't really a tool meant to build Financial Reports... why not just look at some other tools available from the market.. There are quite a few good ones to replace MR2012.
IMHO PowerBI is good to create some C-Level dashboards to show Sales numbers, like top 15 customers of the  months, or Inventory movement, or even other type of transactions.. You might get some global data on the Financials of GP, but I don't think that it should be used as a pure Financial Reporting tool. 
Microsoft provides a free PowerBI Dashboard for GP, but it uses the ODATA services, and those by nature are finicky to get working properly.