The main stats you look for in every player is Goals, Assists, and points. Goals are scoring goals, assists are assisting with the goal scoring, either by passing the puck to a teammate right before the goal or by shooting and your teamate scores off the rebound. Points are a combination of goals+assists.
As a defensemen, you aren't expected to have as many points as a forward, because you stay back more and play defense. While you still want to look at your points, some other good stats to look at are shots blocked, hits, and +/- to indicate how well you are doing on defense. +/- measures every time you are on the ice, how many goals your team scores vs how many goals the other team scores. For example, if your team scores 3 goals with you on the ice and gives up 2 goals with you on the ice your +/- is 1. Hope this helps!