First of all make a known solution of metal of interest and inoculate dry biomass of fungi in metal solution after that at regular time interval analyse the conc of metal AAS(atomic absorption spectrophotometer) also make a control. Subtract the final conc of metal with initial one.
Calcualte the bioconcentration factor just as Mustafa above suggested by using these formula in this website (https://en.wikipedia.org/wiki/Bioconcentration)