It depends on what type of unit those orc warriors are. Strength points give you complete flexibility over how many models a unit of any type contains (so you could have one unit of Heavy Foot represented by four large orcs and one represented by 16 small orcs, with each having 12 strength points). But the number of starting strength points depends on unit type:
Elite Foot: 6 strength points
Light Foot: 12 strength points
Heavy Foot: 12 strength points
Bellicose Foot: 12 strength points
Light Missiles: 12 strength points
Heavy Missiles: 12 strength points
Scouts: 6 strength points.
Ravenous Hordes: 12 strength points
(all from memory)
Most cavalry units have 6 strength points.
The simplest way to represent strength points is one figure, one strength points. But there's no need for that (you could have a single troll representing 6 strength points of Elite Foot or 12 of Bellicose Foot, for example).
The points cost stems from the unit type, not the strength points. So Elite Foot cost 6 points (without upgrades) while Heavy Foot cost 12 and Scouts cost 2. So the cost of your two orc units would depend entirely on what type they were (they could be the same or different, regardless of the number of figures).
If you aren't using one figure/one strength point, you have to track strength points in some way (small dice, tokens, five-bar gates on a bit of paper, etc.).