This takes place in the final section of the level.
The targets you are looking for are standard the silhouetted wooden people dotted around and in the buildings.
There are a LOT of targets - 33 in total. May not seem like much to some, but remember you HAVE to do this with the tank driving around, because as soon as it’s destroyed the mission ends.
Easiest way to do this is on the lower difficulty settings, right at the start of the section. Don’t touch/damage the tank, as it will spawn more enemies to deal with.