How could I get an iPhone from Apple Store?

You cannot. Apple does not have a store for Pakistan, and will not ship an iPhone from a different country to Pakistan.

It appears Mercantile Pacific is now the authorized reseller of Apple products in Pakistan, you can try to buy from them.

I cannot find any authorized resellers listed for your country. You would have to go to a country selling iPhones.

https://locate.apple.com/amei/en/

https://www.valuewalk.com/2019/11/apple-to-sell-iphone-in-pakistan-via-official-distributors-store/