How many units of Botox do I need? (photo)

Hello and thank you for your inquiry and for providing photo reference. You appear to have hollowness under your eyes and Botox unfortunately is not your solution. I would recommend looking into fillers in order to fill out the lack of volume you seem to have . Botox is a muscle relaxent most commonly used for your glabella region, crows feet and forehead. Consult with an injector with years of experience and or a board certified plastic surgeon who can properly assess the best course of action and technique in injecting. In hopes this has helped answer your question. Best of Luck ! 

Many thanks for your question and the photographs. 
From your photographs you appear to have some hollowness under the eyes. This is called a tear trough. This gives the appearance of dark circles and under eye shadows. This would need to be treated with dermal fillers. To achieve the best possible results, it is important that you are treated by a medial practitioner who has detailed knowledge of facial anatomy and experience with injecting fillers. 
Good luck with your treatment.