Try with this way
Right(YeraMonth,4) as Year
Left(YeraMonth,3) as Month
Drop table Source;
This way, Month would be a text field and we should avoid that.
Year(Date#(YeraMonth, 'MMMYYYY')) as Year,
Month(Date#(YeraMonth, 'MMMYYYY')) as Month
Edit: Added a missing 'Y' in the format
Retrieving data ...