The space surrounding a charged object (source charge) is described as having an electric field. The electric field exerts an electrical influence on other objects that enter that space. The electric field value (E) provides a measure of how strong that influence is. The E value at any given location is dependent upon two factors - the quantity of charge (Q) on the source charge and the distance (R) that the location is from the center of the source charge.
 

Some problems in Physics don't involve plug-and-chug. They involve the use of an equation as a guide to thinking about how a change in one variable would affect other quantities. That's the case in this question. The variable being changed from one location to another is the quantity of charge on the Van de Graaff generator (Q .. 2Q .. 3Q). And you need to use an equation (better known as a relationship) to rank the three locations according to their electric field (E). Here's what you need to know about the relationship to do the rankings.

The electric field strength value (E) is directly related to the quantity of charge (Q) on the source (i.e., the Van de Graaff generator). Saying it is directly related means that a larger charge quantity would result in a larger electric field strength. Since the only variable in this question is the quantity of charge, it should now be easy to make the rankings.