Question

how many Puranas.....?

Answer 1

there are eighteen puranas.

Answer 2

Vyasa, the narrator of the Mahabharata, is traditionally considered the compiler of the Puranas.[1] The earliest written versions were compiled during the time of the Gupta Empire (4 - 6 century CE) and much of the material may be dated, through historical references and comparative studies, to this period and the succeeding centuries. The texts were collected from all over India and because of the similarities that are found throughout the texts, it is not possible to trace the line of influence of one Purana upon another, so the corpus is best viewed as a synchronous whole.