There are 29 to 30 days of Ramadan. Every 10 days are called “ASHRA”. Three Ashra Duas are for three tens days. First Ashra refers to first ten days of Ramadan. Second Ashra means next ten days of Ramadan (11 to 20 days) and the third Ashra refers to more next 10 days of Ramadan ( 21 to 30 or 31 days).
There are particular Duas for every Ashra. For example, the Dua for the first Ashra is:
First Ashra Duas
First Ashra includes 1 to 10 days of Ramadan. On these days, we need mercy from our lord.
رَّبِّ اغْفِرْ وَارْحَمْ وَأَنتَ خَيْرُ الرَّاحِمِين
ترجمہ
“اے میرے رب مجھے بخش دے ، مجھ پر رحم فرما، تو سب سے بہتر رحم فرمانے والا ہے”
Translation
“My Lord, forgive me and have mercy on me, for You are the best of those who show mercy.”

Second Ashra Duas
Second Ashra includes 11 to 20 days of Ramadan. These ten days are about seeking forgiveness of all your sins you committed. Remember Allah these days so much and make Dua for seeking forgiveness to all your big sins.
اَسْتَغْفِرُ اللہَ رَبِّی مِنْ کُلِّ زَنْبٍ وَّ اَتُوْبُ اِلَیْہِ
ترجمہ
میرے رب! میں اپنے گناہوں کی مغفرت چاہتا ہوں اور تیری جانب پلٹتا (توبہ کرتا) ہوں۔
Translation
“I seek forgiveness from Allah, my lord, from every sin I committed.”

Third Ashra Dua
Third Ashra includes 21 to 29 or 30 days of Ramadan. This Ashra is about seeking forgiveness to save us from fire on the day of judgement. The Dua to read on these days is:
اللَّهُمَّ إِنَّكَ عَفُوٌّ كَرِيمٌ تُحِبُّ الْعَفْوَ فَاعْفُ عَنِّي
ترجمہ
“اے اللہ تو معاف کرنے والا ہے اور معافی و درگزر کو پسند کرتا ہے تو تو مجھ کو معاف فرما دے. آمین! “
Translation
“O Allah, You are the Forgiving and You love forgiveness, so forgive me. Amen!”

Read Quran Pak here