You might want to look on dedicated manga websites. Some popular ones have the continuation. Also, check if there are any authorized digital manga services available for your region.
You can start from the point where the anime ended. Usually, there will be some indication or discussion in online fan communities about the exact chapter to pick up.
I'd suggest starting from the first chapter of the manga. Sometimes, the manga expands on certain plot points or character developments that weren't fully explored in the anime. This way, you get a more comprehensive understanding of the story.
In some aspects, the 'Classroom of the Elite' anime varies from the manga. For example, some character developments might be emphasized differently or some minor plot points could be omitted or changed to fit the anime format.
Well, the ending of the Classroom of the Elite anime doesn't align straightforwardly with the manga. The manga has its own unique pacing and plot developments that might not match up exactly with the anime's conclusion.