Hi Kaan,
The query operation is meant for exporting multiple values which can only be handled by table. That's why you get error that no output table is mapped.
Your requirement can be solved by implementing Read operation. You just need to make those two properties as key(you can not pass any non-key property as input in Read operation) and pass those two as input and get the third property as output.
Let me know if I did not understand your requirement.
Regards,
Ekansh