I have already earned $996 from one of my client Louise and some more earnings are pending. So, I want to know when this pending earning from this client would come to my upwork account then how much upwork would charge me?
Anisha - look at the Reports page and see what tab the money is listed under. Assuming you're working under a contract, it'll be on one of them. Then mouse over the ? icon for that tab, it will tell you when the money moves to the next tab.
There's also a "When will I get paid" link on the reports page with a lot of detail on the process.