I ordered "Name Servers (NS)" for 3 months for free, what will happen to them in 3 months?

For a domains that are operated at NIC.UA the first 3 months are provided free of charge, after which the order is renewed monthly, automatically and free of charge. If your domain becomes active or you transfer it to another registrar, then the order for "Name Server (NS)" will have to be renewed for money if the order expires. 

For a domains that are not serviced by NIC.UA - the first 3 months are provided free of charge and after 3 months the order must be renewed at the appropriate tariff, which is indicated in the process of renewing the order and choosing a payment period, the renewal cost will be $10 per year. Payments are made in the national currency of Ukraine (UAH) by the exchange rate of the National Bank of Ukraine, all taxes included.