If you finished all the way up to S.3 then I'd say start reading at chapter 190. It's right at the end of S.3 into the beginning of the 1st cour of S.4. If you want to read from the ending of S.4 then start around 248. But you'll miss some chapters on Nekoma and Fukurodani if you do!
What chapter can I read from the anime I finished watching, what chapter can I read??! Thanks for your help I appreciate it