You can make expressions in a query
MyMonth: Month(DateField)
MyYear: Year(DateField)

Then you can either append them as a text, such as
MyCombinedDate: MyMonth & "-" & MyYear

Or if you need it to be a date field for some reason you can DateSerial/Format the appearance, maybe something like this
MyCombinedDate: Format(DateSerial(MyYear,MyMonth,1),"mm/yyyy")

Thank you for your help, I figured out why it wasn't working, I am using the Total function for First and Last Field. Once i turned off the total function the date expressions work fine. I need the total function so I don't see how i can make this work.

Make your totals query, and then make a second query based on that totals query with the date function. See if that lets you get the results you want.