Not that i'm an expert or anything, but it looks like the push-in pillars and plates I used for my project cake in class.
i think you can get different types of pillars, ones which the dowel goes right through, or ones with solid ends, which sit ontop of a dowel. i believe anyway!
Dowels inside the pillars carry all the weight of the tiers. You need hollow pillars.
First of all mark where the pillars are going to be in the cake. Then insert a dowel into each of the marked points and place a pillar over the top. Mark the dowel to cut it to adjust to the height. Remove the pillars and cut the dowels. Replace the dowels in the cake and position the pillars. Repeat for other tiers. Stack the tiers, making sure they are level and centered.
They look to me like pushed in columns...
Here are some Wilton Instructions on how to use them.
Here is what you'll want to use:
And here are instructions on how to use them:
HTH, Good Luck!