Our company works with a USA company. Our company receives our work
payment in USD, recently USD to PKR conversion rate has increased by
15%. But our company still forced a paycut of 50% without reducing
This is something that is happening with many software houses nowadays. While I don't know your specific industry, in many places the speed of developing software was based on future profits from it, it was partial speculation with future money. With the economy taking a very big hit across the globe, there is a lot less money to go around, and such spendings are often no longer viable. While you note that exchange rate has gone up etc, the reality is that you don't know what's going on in the US company, but my guess is that they already announced to your company that there will be a lot less work coming downstream unless prices can be cut substantially. And that's the positive spin, the other, a lot less negative possibility is that the US company simply cut off future projects.
It is, of course, possible that they are also trying to take advantage, but I would say that this notion is a bit naive, as if the economy truly did not impact the industry then their competitors will very quickly poach all the talented people from your company by offering them around-their-previous wages. It's possible that your management is naive to not understand this, but that certainly wouldn't be my first guess.
The point I am trying to make is that this is a complex situation and just because you work as B2B for US company, and the exchange rate has gone up, that does not extend the changes that have happened in the last month and a half. And I hope it will help you to put some context around the 50% reduction in wages across the board - as this is something happening all around the globe. Not in every single company, but it is a widespread situation that will continue to grow for at least a bit longer.
What could be my options in this situation? What can I do in this
First, you need to asses your own situation.
Can you survive on the reduced salary alone, without needing to touch your savings?
If yes, you are still in a reasonably great spot. While you will not have lavish amount of spare cash every month, you are still in a sound financial situation.
If not, if you will keep drawing the needed difference from your savings, how long can you last before not being able to cover the deficit? This will give you a timeframe in which you need to fix this situation. I highly recommend checking some local internet boards for financial and money-saving advice to at least try to make the deficit smaller, checking on money stack exchange can also be helpful, as giving detailed advice about it here is off-topic.
But no matter the result, you need to speak with your boss and understand how long is this pay cut going to last, is there some aid available if this pushes you into a deficit on your monthly budget and try to find out what's the long term strategy for the company to sruvive. If they want to keep the business afloat, they also understand that they cannot have employees who cannot pay their bills, and usually, there are some things that can be worked out - one example (may not be applicable in your country) would leverage some of the tax breaks to pay some of your outgoings as salary sacrifice, lowering the amount of your salary that goes to taxation.
As you noted in the comments, job market is not exactly hot right now, and it may well get worse before it eventually gets better, so it's best to keep the comm lines open with your boss and try to work some deal out that will allow everyone to survive through this.
And at the same time, keep your hand on pulse of the jobs around, send CVs around and maybe you will get lucky. But certainly, plan as if the 50% cut at the current company will be permanent, and when or if it gets overturned, it will be a pleasant surprise.