re: "i have done an hourly job and get paid $42 but its not show on my pending earning neither on my account."
Do you mean to say:
a) "I did an hourly job and I expect to be paid $42. But I have not been paid at all."
b) "I did an hourly job. I DID GET PAID $42. I have received this money. But I don't see the money listed in my "pending payments" box here: Upwork -> Reports -> Overview
c) something else?
re: "How can i get my money back?"
You probably can't get your money back.
re: "Is there any process?"
There is no button you can click, or Upwork "process" that you can go through to get your money back.
The only alternative you have at this point is to contact the client herself and ask her to pay you that money using the Pay Bonus tool.
You could point out that due to Upwork's rules, she does not own the work you did for her and she is now allowed to use it in any way, unless she pays for the work.
If the payment was reversed because the client's credit card payment was declined, then she will need to set up a new payment method in order to pay you for the work you did.
Getting your money back is not a very likely scenario, but you are welcome to try.