lambda to electron volts, can it be done?

I would like to know if and how the the question implied by the following sequence can be answered:

Assumption: space is permeated with energy = Energy (E)

Matter = energy that has been converted to mass (m)

Conversion ratio = speed of light squared (c^2)

Space has volume and energy, matter has mass, energy and volume

Assumption: The volume of space can be converted to mass.

Space at average energy density = E = ~ 10^-29g/cm^3 (lambda)

A tiny particle may have mass of ~ 7x10^-17 eV (possible mass of a photon in electron volts)

What is the volume of space at energy density of 10^-29g/cm^3 that is required to provide the energy equivalent to a mass of 7x10^-17 eV?