In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Its unit is kilogram per second in SI units, and slug per second or pound per second in US customary units. 

the volumetric flow rate, (also known as volume flow rate, rate of fluid flow or volume velocity) is the volume of fluid which passes per unit time; usually represented by the symbol Q (sometimes V̇). The SI unit is m3/s (cubic metres per second). Another unit used is sccm (standard cubic centimeters per minute).

so kg/s to m3/s  this required of to / kg/m3 which is the density 

as I concur with Ayurzana Badarch but  i dont think to use the average density 

rho= sum(Xi*rhoi)

but you need to knew the T and P 

if you need to make an experimental  comparison 

(use a known volume tank a stop watch 

use first only 1 fluid with known density 

then use 2 liquid  and apply the equation.

best regards

Santosh, for these cases I apply the principle of molar volume, this is that a mole (lb-mol) of a gas (At Standard Conditions), is equal to 379.63 cubic feet.

If you know the volumetric gas flow (At Standard Conditions) in cubic feet, you can calculate the molar flow using the value of 379.63 cubic feet. / Lb-mole. Knowing the molecular weight of the gas (lb / lb-mol), you can meet the mass flow of the gas stream.

Likewise, with chromatographic analysis of the current, you can find the individual flow of each component multiplying the whole flow by the fraction of each in particular.

I think in your case, you already know the molar flow and then with the molar volume you will calculate the volumetric flow.

since you have your mass flow rate as kg/s or kg/min depending on the units, if given the density of the material then you use the mass units will cancel each other and you will me left with m3 /s which will be volumetric flow rate

Try PV=znRT.