Yup, Harry was the same when we first started him on cows milk, and actually also when he went from EBM to formula. It was actually really easy - started off with 150mls formula and topped it up with 50mls cows milk, then a couple of days later did 100mls formula and 100mls cows milk - and so on until he was just having total cows milk.
The whole process was a couple of weeks - though it could have been shorter, we just wanted to finish the tin of formula so as not to waste it!
So that should work whether you decide to put him onto the other formula or cows milk