Thank you all for your suggestions.
I was totally over complicating the problem. The solution is simple. In order to use 3 different flavors of huel for a 2 scoop drink I need to know what the volume of the huel scoop is, which is 94cc (according to the bottom of the new white scoops). Then you multiply that by 2 and get 188cc, which is the same as 188mL (according to google, I didn’t know that). Then you divide 188mL by 3 so that 3 scoops will equal two regular huel scoops and you get 62.66mL. Then you convert that to imperial and it is about 1/4 cup (.2611cups). So all I have to do is use a 1/4 cup of each flavor 
I also double checked the Huel forums and found this
And you take 3/4cup and divide it by 3 and you get 1/4cup, so it works out.
Thanks again for all your suggestions.