To find concentration H+ you want to do the inverse log
So 3.5= -log10[x] = 10^-pH
x= 10^-3.5
So [H+]= 3.16*10^-4 M or mol/L
It depends on the concentration of ions which are responsible for the electrical conductivity in aqueous solutions.
the answer its 86.9 .................................
I think it’s D I’m not 100% sure