If you are in an adult ballet class as a beginner or a returning dancer, every exercise you do will prepare you for getting into pointe shoes, if that is your goal. Every ballet barre exercise, whether focused on the feet or not, will get you ready for pointe shoes. The men in ballet can benefit from this viewpoint, as special foot exercises for pointe strengthen, and refine control. This will increase technical accuracy in allegro (jumps) and help prevent dance injuries.
Starting with your demi and grand plies, your use of correct ballet turnout, core muscles, and ease of the upper back, head and arm movements, all means a great deal about everything else you will do in dance class. If you can do this simple (but not easy!) warm up exercise correctly, to YOUR best ability, you will probably be able to do the entire ballet class with the same control. Someday, if not today.
The battements tendus and battements degages, or foot warm up exercises, begin to develop your control and strength in the sole of the foot. While these exercises also make the lower legs stronger, if your calves or shins get stiff and sore, you need to use the feet more, and the lower leg muscles less. Stretch the calves in between exercises with a demi plie or a lunge stretch.
It is good to turn in and allow the rotator muscles to relax in between barre exercises as well.
You actually start preparing for pointe work right from Day One. Everything you do in class will possibly be done later in toe shoes. Any misalignment of posture or weakness in ballet positions, will be magnified when you are on full pointe.
If your ballet studio offers pre-pointe classes, ask if you can view one. You will see special foot exercises being taught, not ballet moves, but just isolated routines to refine and strengthen the use of the feet. If you do not see anything like this, it may not be the best kind of pre-pointe class to take.
Aside from your dance classes, if you would like to gain on the normal time needed to develop a fine classical technique, you can learn the special exercises that target the muscles in the soles of the feet. A few minutes a day is all that is needed. I recommend that you take a look at this fine dancer's guide for preparing to dance in pointe shoes.