What is the prescribed supplication between the two prostrations, and is it permissible to add to it?

It is prescribed to supplicate between the two prostrations with "O my Lord, forgive me," repeated, or "O Allah, forgive me, and have mercy on me, and grant me well-being, and guide me, and provide for me," or "O Allah, forgive me, and have mercy on me, and mend my affairs, and guide me, and provide for me." It is permissible to combine these supplications, and to repeat them, and to add to them anything that does not constitute a sin or severing ties of kinship.