3.4 of a cup of butter is equal to 1 and a 1/2 sticks of butter.
Here's how you measure 3/4 cup:
Check the butter wrapper to see how much it weighs. Often they will have various measurements printed on the packet.
If they don't, or you have already opened the butter and used some of it, then your average kitchen scaled should give you confirmation of the answer you're looking for.
Remember that Clarified weighs less. Often it's only 75% the volume or weight of whole butter!