Hi
This Saturday I am making a cake for a 10yr old girls birthday. It is going to be one 9" deep round with one 6" deep round cake stacked on top and all buttercreamed then covererd in fondant.
My question is this, do I need to use cake dowels in a cake like this since both cakes are not two layers. I am however going to put a filling between each cake.
Never used dowels before and not sure if I need to to in this case.
I think I will put a cardboard cake base under the 6" cake that is to go on the top.
Any and all info is welcomed.

you could probably get away with no dowels, especially since a 1 layer 6" is not very heavy - though it will be covered in fondant. I would probably just stick a couple of dowels under the 6" to be safe, you wouldn't want it sinking into the 9".

It's not difficult - I just use skewers (not the super cheap ones from the dollar store, ones a little thicker than that) and measure how tall they need to be then cut! You would only need a couple, though if you'd rather not I think you would probably be fine!

No, I think you are right, I would rather be on the safe side and yes the fondant does add weight for sure.
Thanks for the tip.

Being safe rocks.

Definitely dowel support the 6 inch cake on a round cake board. I'd use 6 lollipop sticks, this is what Toba Garrett uses. They are super easy to cut with a pair of dykes. I'd enjoy using the long skewers as a center dowel as Renea says. I normally only use one and again, it's super easy to cut with a pair of dykes. Your cake is going to be surprisingly heavy.