There is no problem in pursuing for LLB after studying PCMB in class 12th. You can pursue whichever stream you like the most.LLB can be done in two ways- After class 12th 5 year integrated BA LLB course, After the graduation 3 year LLB. Some of the entrance through which you can take the admission are-

CLAT, CET IPU,CUSAT Cochin, AMU Aligarh, Law CET Andhra Pradesh. You must be 12th passed with minimum 50% marks with recognized board. Rest eligibility criteria you can read on the official website of the college and from the entrance details.