It seems you pretty well understand how to find the pairwise forces and you are just having trouble adding them to get the net force. Since the forces are vectors, you need to add them like vectors. I assume this is difficult to imagine because you are just learning what a force is and you are just learning what vector addition is.
So think about something you are more comfortable with. Imagine that you have a vector displacement to the north and another displacement to the east. Now try to add them to get the net (that is, total) displacement. You should get something to the northeast. Now you just apply the same reasoning to the force vectors. The pull to the north adds with the pull to the east to give you a pull to the north east.
As you would find with the displacement, there are two ways of representing this resultant vector. You can give the components along the north and east directions (in which case the picture you gave is already a compelete solution), or you can give the magnitude and direction. I recommend you try to do it both ways.
Another relatively minor point is that you should be more careful about your units.