If I have a fixed aircraft as the baseline, then I am not sure the specific flight condition, can I use the load factor to estimate the lift on the wing?
If you know where the CG is, and where the aerodynamic centers of the wing and the tail are (I am assuming a traditional configuration) so you know the distance from the aero center of the wing to the CG = d_wing, and similar for the tail, and you know the moment the wing generates (ignore the moment about the tail...it is small), and you know the load factor, then you can figure out the total lift generated by the wing. You have two equations:
Sum of moments about CG = 0 (constant pitch rate)
d_wing x liftWing + d_tail x liftTail + wingMoment = 0
Sum of lifts equals load factor times weight of aircraft
liftWing + liftTail = loadFactor x weight
Now solve for liftWing.
If you mean total lift force, then yes you can as Lift = Load Factor * Aircraft Weight.