The number of satoshi per bitcoin is 1e8 or 100,000,000, so if you have a fiat value per bitcoin such as $7000/BTC, the calculation is:

$/satoshi = $7000/1e8 = $0.00007 per satoshi

Of course, there is no fixed fiat to satoshi value because the fiat value of Bitcoin is determined by the market, i.e. exchange value.