It is not possible to have Query compare one field to another on a record to return results.
This would require a query to locate Constituent records that have a Maiden Name.
Then create a Constituent export to Excel that has output of both the Last Name and the Maiden Name.
Create a formula in Excel to compare the Last Name to the Maiden Name to determine if they match.

NOTE: Creating formulas in Excel is outside the scope of Blackbaud Product Support.