Here's how to figure out the number of atoms in the molecule 3CO:

* CO: This represents one molecule of carbon monoxide. It contains 1 carbon atom (C) and 1 oxygen atom (O).

* 3CO: The '3' in front of CO indicates that there are 3 molecules of carbon monoxide.

Therefore, 3CO contains a total of:

* 3 carbon atoms (3 x 1 = 3)

* 3 oxygen atoms (3 x 1 = 3)

In total, there are 6 atoms in 3CO.