Ina lillahi wa inaa ilayhi raajioon. May Allah grant you and your family sabr during this difficult time, and may Allah forgive him for his sins and admit him into Jannah tul Firdaus. Ameen.
I understand how you feel, as my father passed away a few weeks ago now.
One du'a that you can read is this:
اللَّهُمَّ اغْفِرْ لَهُ وَارْحَمْهُ وَعَافِهِ وَاعْفُ عَنْهُ وَأَكْرِمْ نُزُلَهُ وَوَسِّعْ مُدْخَلَهُ وَاغْسِلْهُ بِالْمَاءِ وَالثَّلْجِ وَالْبَرَدِ وَنَقِّهِ مِنَ الْخَطَايَا كَمَا نَقَّيْتَ الثَّوْبَ الأَبْيَضَ مِنَ الدَّنَسِ وَأَبْدِلْهُ دَارًا خَيْرًا مِنْ دَارِهِ وَأَهْلاً خَيْرًا مِنْ أَهْلِهِ وَزَوْجًا خَيْرًا مِنْ زَوْجِهِ وَأَدْخِلْهُ الْجَنَّةَ وَأَعِذْهُ مِنْ عَذَابِ الْقَبْرِ أَوْ مِنْ عَذَابِ النَّارِ
I heard it from 'Auf b. Malik that the Prophet (ﷺ) said prayer on the dead body, and I remembered his prayer:" O Allah! forgive him, have mercy upon him, give him peace and absolve him. Receive him with honour and make his grave spacious; wash him with water, snow and hail. Cleanse him from faults as Thou wouldst cleanse a white garment from impurity. Requite him with an abode more excellent than his abode, with a family better than his family, and with a mate better than his mate. Admit him to the Garden, and protect him from the torment of the grave and the torment of the Fire." ('Auf bin Malik) said: I earnestly desired that I were this dead body.
Sahih Muslim Vol. 2, Book of Prayers, Hadith 2104 https://muflihun.com/muslim/4/2104