Michaelis-Menten equation; how to find the constants from enzyme activity experimental results?
Have you got data for different concentrations of hydrogen peroxode?

If so you should choose a time point that falls on the linear part of your time graph. And plot the rate at that time point for each substrate concentration. 

That will give you a MM curve where you can calculate the values you desire. You cannot calculate them with just your time data that you have provided.