How do you re-structure duplicate URLs which were already indexed by search engines?

I am facing duplicate content issue. I want know about the best solution to removing duplicates We have 19 education levels which are attached with 200 categories please see following URLs. 19*200 = 3800 URLs e.g: 1. /abc/education-8-class. 1. /cds/education-8-class 2. /abc/education-9-class. 2. /cds/education-9-class 3. /abc/education-10-class. 3. /cds/education-10-class 4. /abc/education-11-class. 4. /cds/education-11-class 5. /abc/education-12-class. 5 /cds/education-12-class 6. …………….. ……………………… 7. ……………. …………… But for above URLs, same content is rendering. I want to remove all class level which is no more useful e.g (-8-class) from URLs And I want to keep correct URL 1. /abc/education, 2. /cds/education Now my actual URLs will be 200. I am not able to select which method will be good from SEO point of view. 1.404 2.301 redirects 3. Canonical Tag Or any others please suggest me