Change number of river items

Could you help me where is the file that I can change the number of intes of the river in the main page? Has 20 items, I would like to increase but I do not find the file. Should be a plugin like others but I do not think so. I'm a beginner. I just need to know where the file is. Change with & num = 40 limit => & num
Beginning Developers

Beginning Developers

This space is for newcomers, who wish to build a new plugin or to customize an existing one to their liking