I have build my own bridge from paper and i want to know the elastic module for the bridge, my bridge is flat all over the way and cylindrical from the sides.
Elastic Modulus is a property of material, not the shape of the structure.
In your case it depends on the type of the paper you used and also weather the bridge walls are parallel to the paper fiber grain or perpendicular, or angled, because paper is not an isotropic material.
Most likely the paper you have used is composed of randomly mixed fibers, which means it does not have a consistent modulus of elasticity regardless of the direction of stress.
You can test the modulus of elasticity of you paper by hanging a weight at the end of a narrow strip of the paper say 1/4 inch wide by 3 feet long and measure how much it elongates; then edit your question with these results. we can then help with an estimate of the E. If you detect a grain repeat the test for strip parallel and perpendicular to that. you need to be judicial and careful in setup and measuring, may be first let the weight hang for few minutes and use a vernier.