Dear Rosalia, as u have taken 0.2g (200mg) sample and added in 9.8 ml solution.

The dilution factor is=9.8+0.2g sample/wt of sample.

This comes out to be 50. Now CFU/g=no of colonies on a plate × dilution factor ÷vol.of sample taken for plating. For CFU/ml u will have to multiply the value with 10 as u have taken 0.1 ml sample for plating. I hope you must be able to calculate both CFU/g and CFU/ ml