How is carbon monoxide a compound

Yes.

The formula is CO (C is carbon and O is oxygen). Each molecule consists of one carbon and one oxygen joined together. It is not an element, but is made of two elements, carbon and oxygen, joined together. It is also not a mixture as you can't separate out the carbon from the oxygen as the two are joined.

Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. It is the product of the incomplete combustion of carbon-containing compounds, notably in internal-combustion engines. It consists of one carbon atom contently bonded to one oxygen atom. It is a gas at room temperature.