Concentration cell lower half cell concentration from measured cell potential

I am trying to find the Ksp of silver thiocyanate:
AgSCN(s) --> Ag+ (aq)SCN-(aq)


but I need to first prove that the **lower** [Ag+] = 1.27-12 M, but don't know how to find it. 


The data I am given:
Volume of 10-4 M Ag+ solution used: 10.00ml


Volume of 1.0 M KSCN added: 50.00ml


Measured cell potential when an Ag(s) electrode was placed into the above mixture, and then joined to the Ag+(0.1M)/Ag(s) half cell: 0.645V


Results:
Calculated lower [Ag+] from cell potential: 1.27-12 M


I am suppose to use this equation for the concentration cell:


![enter image description here](https://i.stack.imgur.com/eVZRd.gif)


where n is the number of electrons.


So really my question is how I would go about finding the higher concentration of Ag+ and then use that to determine that **lower** [Ag+] = 1.27-12M


