mu = log(m), where m is the scale parameter. So if mu = 0, the scale parameter = 1. Sigma, or shape parameter, equals 7.85. We also need to know theta, or the location parameter, which is the x value of the distribution relative to the the standard lognormal distribution. You can then put these parameters into f(x), or the general formula for the probability density function of the lognormal distribution, to obtain your expression :)