$$H_2C_6H_6O_6(aq) + 2NaOH(aq) \rightarrow Na_2C_6H_6O_6(aq) + 2H_2O(l)$$

Total ionic equation:

$$H_2C_6H_6O_6(aq) + 2Na^+(aq) + 2OH^-(aq) \rightarrow 2Na^+(aq) + C_6H_6O_6^{2-}(aq) + 2H_2O(l)$$

Net ionic equation:

$$OH^-(aq) + H_2C_6H_6O_6(aq) \rightarrow C_6H_6O_6^{2-}(aq)+ H_2O(l)$$