Where does one buy herbs dry or fresh for making herbal tea?

preferably medicinal herbs for curing prostate cancer

I found this:
"Traditional Chinese Medicine (TCM) Approach to Prostate Care

TCM associates hyperplasia of the prostate with damp heat and kidney deficiency. After the age of 40, one's vital energy in the kidney system decreases, resulting in the disturbance of sex hormones. This process also decreases one's sexual energy, which affects the function of the prostate and the circulation in this region. Throughout the ages, in order to compensate for the decline of prostate function, men in China have used regular acupuncture treatments to improve the circulation and energy in the prostate. To enhance the effect of acupuncture, they have also used Chinese herbs such as He Shou Wu, in traditional, custom herbal formulas to replenish the kidney essence. Kidney essence nurtures the prostate. As the prostate is revitalized, it is now capable of self-regulating toward normal functioning and maintaining a balance of growth and non-growth. This is the balancing properties of Chinese medicine.

Diet and Lifestyle Recommendations

TCM nutrition encourages men to eat more nuts, seeds, pumpkin, mushroom and berries to help nourish their prostates. Managing stress, regular exercise and massaging the prostate are also vital to help maintain prostate health. Besides Chinese herbs and western herbs such as saw palmetto, there are many delicious foods that you can eat to help maintain a healthy prostate. Regular consumption of foods that contain lycopene (a prostate protective antioxidant) is highly recommended. The following are foods that contain lycopene: watermelon, pink grapefruit, guava, papaya, apricot and cooked tomatoes (tomato paste, tomato soup, tomato juice and marinara sauce). Nutrition experts have expressed concern that pesticides and herbicides in animal products may trigger cancer growth. This may be another good reason for you to eat more organic fruits and vegetables and avoid saturated, high-fat animal products and snacks that contain hydrogenated or partially-hydrogenated oils. These diet and lifestyle recommendations may help prevent this pervasive cancer and help invigorate your body."

Shop selling organic products

Check with organic stores such as Whole Foods. Not sure of your location, but if that proves futile, try places like Vitamin World and other herbal medicine stores. And good luck.

some where in a store

We have a herbalist in our town. Practices herbal medicine.
We also have a shop that sells vitamins, and herbs. If you
look in the yellow pages under herbalist you might find what you are looking for. Good Luck!