Say the dua 7 Times:
اَللَّهُمَّ أَجِرْنِيْ مِنَ النَّارِ
Pronunciation
Allaahumma Ajirni minan-naar
Meaning
O Allah, protect me from Hell. Harith ibn Muslim (RA) said: The Messenger of Allah (ﷺ) said to me: When you finish the maghrib prayer, say: 'O Allah, protect me from Hell" seven times; for if you say that and die that night, Allah will protect you from jahannam; and when you finish the fajr prayer, say it in a similar way, for if you die that day, Allah will protect you from jahannam. Most of the muhaddithin have considered this hadith to be acceptable.
Source: Hasan (Ibn Hajar). Al-futuhaatur Rabbaniyyah 3/69
Duas from IslamicAPI's Masnun Dua dataset (based on the Quran, hadith, Hisnul Muslim and Rahe Belayat). See the dataset