Prores lighter files? (help)

I have noticed that prores files work much faster on my pc than mp4 h264. I have more than 300 videos between 3-10 seconds. I convert them to prores, but they are too heavy. When they were mp4 they weighed 5mb each. Now they weigh more than 200mb and I don't have that much space. How can I create lighter prores files with Media Encoder?