How many holes are there on a connect 4 board?

The vertical panel has 42 holes in it (7 rows of 6 vertical holes) and you are given 30 red counters and 30 green counters.

https://en.wikipedia.org/wiki/Connect_Four

Unless you are referring to the 2d computer version, you forgot the big hole you put the counters in at the top and there are holes on both sides. Some have a covered hole at the bottom for emptying the counters when you have finished. So the answer would be 85 or 86 if you have the deluxe version which empties at the bottom.