What he said^
Don't think of the game as giving you missions that require you to go to a specific place in order to complete them. Think of missions instead as a series of 'requirements' that need to be fulfilled. How you go about fulfilling them is entirely up to your own imagination and very much down to your creativity and ingenuity.
If the mission is to kill 4 traders, then go and "kill 4 traders"
Tip: traders will be flying a 'lakon' type ship (lakon 6, 7 or 9) or a hauler. You won't find a trader in a Viper, a Cobra or a Sidewinder e.t.c. A trader will also have a cargo full of some random commodity and will usually be a member of a faction that has a name that sounds quite 'trade centric'.