On this page of the guide, you will learn how to get a jam during Minuteman's first story mission in Mr Prepper.
Minuteman will ask for a jar of blueberry jam in one of the letters, starting a series of story quests. Deliver it to unlock the next quest and an important merchant – Gourmet. To make a jam, you will need a glass –dismantle a cup from the kitchen.
You also need sugar and berries. You will buy sugar in the Supermarket (or you will make it from beets after drying them on the dryer). Collect berries in the Forest level 1. Finally, combine the ingredients on the stove by selecting the correct recipe from the list on the left and send the jar to Minuteman – open the trading panel.
Alternatively, you wait for a jam to be sold at the Supermarket. However, it is quite expensive - $29. This is a lot of money, especially in the beginning.