فَإِنْ لَمْ يَكُنْ لَهُ مَا يَذْبَحُ صَامَ ثَلَاثَةَ أَيَّامٍ فِي الْحَجِّ وَآخِرُهَا يَوْمُ عَرَفَةَ
Translation: If he has no sacrificial animal or means to offer one, he fasts three days during Hajj, the latest of these being the Day of Arafat.
These fasts operate as a substitute when the pilgrim cannot provide the required offering. Al-Quduri gives the Day of Arafat as the latest point for the initial three. One should not assume these can simply be postponed until after the Day of Sacrifice.