Tira here, from Shopify.
Shopify Payments is currently available in specific countries, you can view the list in our help docs here: Shopify Payments Requirements. Pakistan is not one of the eligible countries. You can find payment gateways in Pakistan by checking out our list, here: Ways to accept payments in Pakistan.
Is there a particular reason you're looking to have Shopify Payments on your store? What payment gateway are you using right now?
If you could let me know, I would be happy to send this as feedback to our developer team, so that we can improve our platform for you and all of our merchants.
I look forward to hearing from you!