Hello Archana,
Its good to hear that you have been planning to go for CA course and make a career in the CA after your Bcom.  The students who have completed their Graduation or who are going to complete can apply for the CA course through the Direct Entry Scheme. Under this scheme a student who has completed Graduation from Commerce need to have at least 55% marks in the graduation and should have studied any 3 subjects of 100 marks each - Accounting,Auditing,Costing, Taxation, Management Accounting, Business Administration.
After taking an admission under the Direct Entry Scheme a student can complete the CA course in 3 to 4 years. Whereas you also consider the 3 years of Internship. If we count together it will take around 5 - 6 years to complete the CA course.

Hope this info is helpful!!!