adjusting length of home page to control number of posts

Please advise. I believe this plugin was the one I used at one time to adjust the length of my HOME PAGE by modifying numbers. In other words, I could control number of posts displayed. However, I believe some glitch has occured and I no longer see this plugin feature available to me in my POSTS sidebar menu item.

Can you assist or advise. I am a new user and an old codger, so please keep it simple.