You may see some mild improvement with your scarring and freckles, although IPL or BBL photo rejuvenation for the freckles, and laser resurfacing with an ablative fractionated laser such as a Profractional for the scarring would be far more effective (since deeper).
Microdermabrasion is a great topical treatment to smooth out your skin and treat mild acne. However, it will do nothing for ice pick scars and freckles. The best treatment for these types of scars and freckles is the Fraxel laser. The 1927 wavelength of the Fraxel will remove all of the hype pigmentation. The 1550 wavelength will treat the scars but will take 4 to 5 treatments depending on the depths of your scars. Please find a board certified dermatologist with a great deal of experience with lasers for the best results.