Should I fast the day of Arafah on the 8th in Pakistan, which corresponds to the 9th in the Kingdom, or should I fast according to Pakistan's date?

The correct view is that sighting the crescent moon differs according to the variations in moonrise locations. Each country has its own ruling. If the crescent moon is sighted in one place, it does not obligate all Muslims to act upon it. Rather, the matter refers back to those with knowledge. If the moonrise locations coincide, then they become like a single country; otherwise, they do not. This is what is necessitated by the Qur'an, the Sunnah, and analogy, based on the Almighty's saying: "So whoever sights [the new moon of] the month, let him fast it," and the Prophet's (peace be upon him) saying: "When you see it [the new moon], then fast, and when you see it, then break your fast." However, if two countries are under one rule and the ruler commands fasting or breaking fast, then obeying his command is obligatory.