At first thought you can try something like this
dateTime( parseInteger($InputMetaObject_1Object/ExpectedYear), parseInteger(toString($InputMetaObject_1Object/ExpectedMonth)) )
However, the dateTime function doesn't accept variables as input. So you need to do create a String representing the date. This string can be parsed into a date.
parseDateTime( $InputMetaObject_1Object/ExpectedYear + '-' + toString($InputMetaObject_1Object/ExpectedMonth) + '-01', 'yyyy-MM-dd')
Note that you for parsing the enumeration
ExpectedMonth into the right month number you need to specify the values of this enumeration as follows:
You can look here for the specific microflow expresion that you will need to convert the three values into a datetime format: Microflow expressions.
At 'date values' you will find this expression, which should do the trick: Input: year, month, day dateTime(2007, 1, 1) "Mon Jan 01 00:00:00 CET 2007", you will probably need to convert the enumerations to strings first.