I am making a lady bug on top of my 8" and want it to be 3D not flat what should I use?

Depending on how big you want it, you can use 1/2 a ball pan or 1/2 a mini ball pan or even a cupcake. Shape it as needed and cover with bc and fondant or gumpaste.

Yup...jgifford is correct..Use a mini ball pan...it makes a cute lady bug topper!!

Rice cereal treats would work, too. Especially if you don't have the mini ball pan.

I used a 4 in pan and just carved it to shape then covered with fondant. Then that was the bd girl's own personal cake.
http://cakecentral.com/gallery/1962440

I took the easy way out and used a Hostess Snowball Cake. I peeled off the marshmallow piece, and covered it in fondant.

Easy!

I just made a cake like that this weekend! I used the Wilton ball pan, and just put half of it on the cake. Because it wasn't carved, it was so easy to ice!

Or a small pyrex bowl would work.

I have some small stainless steel mixing bowls that I use for making the dome shapes (sometimes my ball pan is just too large). Anything that's oven-safe and approximately the right size and shape is fair game when it comes to cakes.

I used the sport ball cake pan for my lady bug. I made it will the smaller insert, not the large ball one, and it worked really well. For the head of the lady bug, I just molded MMF and attached it to the body that I had already covered in MMF.

http://cakecentral.com/gallery/2153389