In my mri scan report it shows complex grade 3 posterior horn medial meniscus tear and high grade acl tear.but there is no locking and poping sound and there is no pain while doing any activity like climb stairs,walking,running,is surgery require?

This is a judgement call, as depends upon knee stability and likelihood of progressive healing associated with conservative therapy. The big issue is the potential development of "wear and tear arthritic degeneration" (chondromalacia). At your age, 21 yrs, you have potential for worsening over the years. Obtain at least 2 orthopedic surgical consultations and decide.