Is the Pico laser for the body effectively whiten dark pigmented skin? (Photo)

no pico will do very little and take so many treatments. looks like you have acanthosis nigricans which will never be cured. you can do enlighten and cosmelan peels, viivatia foam, and restorsea 10x to help but rubbing typically (unless you have diabetes are overweight) is what causes this (see link to emeragecosmetics.com where we do free skincare consults daily). you need hormonal optimization most often (see dr jill stocker at "about" on jasonemermd.com as she helps this through internal hormomal optimization).
Hyperpigmentation from any type needs a combination approach of peels like cosmelan,  lasers like clear and brilliant and aerolase or laser genesis, radiofrequency like venus viva, and constant skin care and sun protection.  Bimontly facials with silk peel dermalinfusion is essential to hydrate, exfoliate and infuse vitamins and antioxidants into the skin.  If you have acne you can do additional treatments and peels to get more improvement.  I suggest a formal consultation with an expert in lasers and peels. Best, Dr. Emer.