TEM to get an average particle size of AgNP. If you you centrifuge some i.e. 100 ml of solution- dry - melting - to get accurate amount of silver, you can back calculate # of particles.

If your Ag NP was successfully capped with PVP, in TEM analysis you would expect a formation of a layer of PVP shell around the Ag NP, conduction the EDX on the layer of shell could confirm the coating process..Depend on the agglomeration and dispersion effect of your Ag NP, the concentration of the AgNP in the redispersed solution may not be representative if tested by AAS, ICPOES if agglomeration did occur..Therefore, TEM should be conducted to get the nanosize of the AgNP, and  ensure successful coating since the size of NP and coating may effect its disersion ability in the solution.

Good luck..

Using TEM or AFM

In fact this is not a simple question as silver can form something like d/a bonds with nitrogens of PVP. To find a real silver content in the dispersion, the weighed dry portion of the PVP stabilized AgNPs should be freed from PVP. You can find how to do this e.g. in a good paper Article Removal and Utilization of Capping Agents in Nanocatalysis

Just in case check the cleaned NPs by e.g. FTIR or other method if all PVP has removed. If not, you can try these cleaned NPs further to heat in pyridine to replace PVP leavings by pyridine which is further can be easily evacuated.

Using TEM.

Removal of PVP from Ag nanoparticles' surface can be done by stirring the particles in aqueous HCl or KI solution (0.05 M) for about 3 hours. Typically, 250 uL of 4mg/mL nanoparticles can be stirred in 2 mL of HCl or KI solution (0.05 M). Afterwards, you can check again the weight of Ag NPs. --------------------------------- High quality Silver (Ag) nanocubes and Surface-enhanced Raman Scattering (SERS) substrates available at: https://silverfactorytechnology.com/