I used to work and my employer has paid my maternity insurance (assurance maternité). At the moment, I am jobless and will give birth to a baby. How should I claim for this insurance?
How does it work here?

That's a general question, have you done "the homework"?

All the information you need (Allocation maternité)
Additional rules/support for canton Geneva

You have to have paid AHV/IV roughly since the conception and it is required that you work 5 months during the pregnangcy as an independent or employee to get the insurance. Since you have no employer at the moment, you have to contact the compensation office directly. You can find the form and further details with the first link.