Short, conventional answer: No.
Long, more accurate, but also potentially confusing answer: Not generally speaking. As many pagans will point out with varying degrees of huffiness, Satan – the Adversary figure of Christian, Judaic and Islamic doctrine (I’ll call these the Abramic religions to save time) – doesn’t figure in most pagan traditions. Many modern pagans, especially in the USA, are highly sensitive to the accusation of devil-worship, and are quick to point out that Satan is a part of these monotheistic faiths and exists in his modern form solely in order to explain the undeniable presence of evil in a world created by an entirely good deity. (This is despite the explicit co-operation between God and Satan that’s evident in the biblical Book of Job.)
Still, it’s not wholly accurate to say that pagans “don’t believe in Satan”. At least, it’s not universally so. Bearing in mind the complex web of definitions for the word ‘pagan’, there are some pagans who recognise Satan as one deity amongst many. There are also the Satanists, who interpret Satan’s nature somewhat differently from the standard Christian perspective, who might be classified by some Abramists as pagans, and might in some cases label themselves so. In general, though, Satanists aren’t thought of as pagans in the sense that we’d use the word.
And it’s also fair to point out that many pagans, especially those of a reconstructionist or historical slant – that is to say, those who follow the pagan religions of ancient cultures – recognise at least one entity responsible for ‘mixing things up’. It’s simplistic to associate ‘trickster gods’ with ‘evil’ – they’re not evil any more than they’re good; but it is their responsibility to inject chaos into proceedings and, from our delicate human perspective, this sort of thing can certainly feel evil.
There are also some (admittedly uncommon) strands of modern pagan belief that recognise the presence of evil in the world, and reason that, just as there are gods of love and peace, there must also be gods with dominion over the rather nasty things humans tend to do to each other. Given that this is essentially the function served by the New Testament Satan at least, the argument then is only whether these gods are actively worshipped, or merely respected as one should respect anything capable of doing horrible things to one.
Did that help?