If you have an active NPC Missions, use the Burger menu on the left - then when the menu appears on the right you will see ‘NPC Mission Log’
Click that - choose the mission on the left
On the right you will see the 'instructions / mission brief and some Icons at the bottom.
In most cases there will be an Initial NPC Icon. Mouse over this.
Tells you the NPC Name AND location / System. You will also note that hovering the mouse over the other icons will give you quick info on what your meant to be doing and where (if needed) items need ot be taken etc.