As a general guide, select a winch with a maximum line pull of 1.5 times greater that the Gross Vehicle Mass (GVM) of the vehicle or a Gross Combination Mass (GCM) if towing a trailer or van.
You should also take into consideration the total load being carried including accessories & equipment, the general terrain, gradients and how often it will be used.

Vehicle Only – 3,000kg x 1.5 = 4,500kg                                     Size: 9,500lb/12,000lb
Vehicle with Trailer – 4,000kg x 1.5 = 6,000kg                       Size: 12,000lb

Always remember that a winch’s pulling capacity is rated on the 1st layer, the more layers of cable on the drum reduces the pulling capacity of the winch. A great way to increase the pulling capacity of a winch is to use a snatch block; they provide a significant mechanical advantage over a single, direct line pull recovery, when used correctly.