Since you didn't specify which compound that has that molecular formula you're interested in, I'll show you how to find the number of pi bonds for hexamethylbenzene.
Here's how the Lewis structure for hexamethylbenzene looks like
Notice that the molecule has 3 double bonds. Each double bond actually consists of a sigma and a pi bond, so that means that you have a total of 3 pi bonds, one from every double bond, present in the molecule.
When trying to figure out how many pi bonds a molecule has, keep in mind that
- Each double bond contains 1 sigma and 1 pi bond;
- Each triple bond contains 1 sigma and 2 pi bonds.