An out of the box GoldMine implementation does not store the "firstname" separately anywhere.
Some of our clients happen to have it stored in the "Dear" field, but that's customer-dependent and not everyone does such.
Where are you running this query?
Where is "firstName" coming from at the end of the query? (firstName is not a standard GoldMine field name.)
Most GoldMine implementations store the full name in the contact field, so it is essentially the first name and last name with a space between (unless the middle name comes into play). Therefore, searching by contact is essentially searching by "first name, last name", as you've asked (excluding the comma).
thank you for your response.
I will look further into this and I will keep you posted if I have issue