Hello Rashi, 

PU can refer to all 3 Punjab , Pondicherry and Poornima University. But since Punjab University is the most common, I am assuming your question is about PU, chamdigarh. In Punjab University, admission to BSC courses is done on the basis of their common entrance exam called PUCET.  You will get admitted based on your merit as scored in the PUCET.  To apply to PUCET you only need to have a 10+2 certificate with the subjects physics,  chemistry,  maths,  biology, english. Usually they set the minimum aggregate at 50% so with your marks you can easily apply. 

Hope this helps :)