Best way to increase milk supply

I have been pumping for a month since i gave birth last month. Milk is getting lesser and lesser. I had to mix feed my baby, mostly formula since my supply is so low. Today after 45mins of pumping i only had 5ml. #pleasehelp I really need to know what is best to increase my milk supply. Also if i consume lactation cookies, after how long does it kick in for me to be able to pump?