I submitted one of my research paper in a fake conference by mistake. Now I want to withdraw my paper from it, But I am facing problem in withdrawal as no email id is given on that website. The problem is that now my paper has been accepted by another conference. But according to Turnitin, my abstract is already published somewhere else. Does anyone here know how and where to report such fake conferences?
There is no legal or ethical reason not to submit the same paper to multiple conferences, provided you did not agree not to do so when you submitted the paper. However, apparently in some fields there may be unspoken, unwritten (and to my mind unjustifiable) expectations that you will not submit your paper to multiple venues. Hence, if you're in such a field, you should follow the herd, because they will punish you for not doing so.
However, in other disciplines (especially in the humanities) where conference proceedings are not normally published, the expectation is that a paper is presented at a conference in order to solicit feedback in order to make the final, published version of work as good as it can be. And in such fields, obviously, nobody would hold it against you trying to present the paper in as many different venues as possible, in order to get as much feedback as possible.
My view is that if the scam conference wishes to publish your paper in its proceedings, but did not announce this to you when you submitted, then you have no obligation to sign a copyright transfer agreement allowing them to publish it and I think you can safely tell the other conference that you've withdrawn your paper from the scam conference. Of course, if you're in a field that penalizes people for this sort of behavior, it would be imprudent of you to do so, even if there is no general obligation not to.
On the other hand, if you did sign such an agreement with the fake conference, then you are just going to have to accept that they own the copyright to your paper, will publish it, and accept this situation as a valuable lesson on knowing your venue.
Speaking more directly to your current circumstance, where you might have violated an unspoken norm (or might not have, depending on field). If the good conference asked you to certify, when you submitted, that the work wasn't under consideration elsewhere, then I think your best bet is to write immediately to whoever is in charge of the good conference and explain the situation in detail. Unfortunately there is a proliferation of scam journals and fake conferences these days, so it may be that the organizer of the good conference is sympathetic to your position. Don't expect a positive response, exactly, but the sooner you let the relevant people know the situation and ask their advise, the better the outcome is likely to be.