I have a large abundance of farmers which aren't really needed, so I'd like to switch them to things I'd find more useful. However, I'm not really sure where to do this. Googling the issue told me to select a dwarf and press 'p' for labor settings, but that option is not present. Here's a screen-shot of my dwarf's selection screen:
I'm not really sure what to do at this point, as I've got an enormous amount of food but all of my other endeavors are proceeding very slowly.