Hi Aspirant,

You can pursue any course after Bachelor of Science. But you have to start Law programs from scratch. The National Level Entrance Examination for Law Programs is CLAT Examination (Common Law Admission Test) and AILET ( All India Law Entrance Test). Both the examinations are conducted by National Law University Delhi. The course Duration for Undergraduate program in LAW is for 3-5 years.

If you feel you have selected wrong field, you still lot of time to change your field. as there is no age limit for Law examinations. I have attached more details of LLB  ( Bachelor of Legislative Law) Eligibility, Fees, Colleges etc below, You can refer them. Hope you find this information helpful. All the best for your career.

https://www.careers360.com/courses/llb-bachelor-of-legislative-law