Can I ventilate attic space using wall vents?
Gable end vents were a common approach to attic ventilation decades ago, but those aren't nearly large enough. Gable vents don't provide the airflow that a soffit-to-ridge system does (via convection and vacuum), so they need to be quite large. A vertical loop is much better than the strictly horizontal circuit gable vents provide.

A rule of thumb is 1 square foot of ventilation for each 300 square feet of attic area. This number is typically used for soffit/ridge ventilation, though. What you actually need depends partly on the layout of the building, and whether some areas of the attic are remote with respect to the closest vent.

Then there's the fact that the vent in question doesn't offer much weather protection. Most gable vents are louvered, so that rain drains off even when driven by wind. You don't want your attic wall and the ceiling below rotting out due to regular wetting.