The number of bags of cement that you will need for 3 cubic meters of concrete will depend on the strength of the concrete that you are trying to achieve and the proportions of the other ingredients in the mix.
As a general rule, it takes about 1 bag (50 kg) of cement to produce 1 cubic meter of concrete, so you will need 3 bags of cement to make 3 cubic meters of concrete. However, this is just a rough estimate, and the actual amount of cement that you will need may vary based on the specific mix design that you are using.
To determine the exact amount of cement that you will need for your concrete project, you will need to consult a concrete mix design or use a concrete calculator. These tools will allow you to input the specific details of your project, such as the strength of the concrete, the size and type of aggregate, and the water-to-cement ratio, to calculate the precise amount of cement that you will need.