It depends on the shape, whether it gives you the dimensions or not, or whether you can divide it up into separate shapes.
Fill
You have not provided the dimensions of the cinder blocks. 8 by 8 by 16 in what units of measurement?
Many shapes can make up a heptagon, as long as there are always seven sides. (They do not have to be of equal length.)
Two Rhumbuses Make up a parrellogram.
A triangle has 3 sides and 3 inside angles that add up to 180 degrees. If you are asking about physical dimensions, a triangle is a two-dimensional shape.
There are 4 triangles that make up a pyramid. 4 on the sides and on the bottom a square or rectangle.
2D is a shape or an object that is flat and u can not pick it up, and it has 2 faces. 3D is a shape or an object that is a shape and you cant pick it up and hold it, and it can have as many faces.
It depends on the shape, whether it gives you the dimensions or not, or whether you can divide it up into separate shapes.
A point. It has zero dimensions. It has no length and no width - only a position.
You can't tell the dimensions from knowing the volume. The tank could be in the shape of a cube, a long skinny box, a sphere, a teardrop, a cylinder standing up with flat top and bottom, a cylinder lying down with round ends, etc., and every shape would have different dimensions for a volume of 1,000 barrels.
In three dimensions, it is called an octahedron. The flat shape with eight sides is an octagon. You can look it up in Wikipedia.org
There are many things that make up a prism. Such as glass, light a it has to be in a certain shape to have the light pass through it.
The constellation Camelopardalis consists of many stars, but there is no specific number as the stars within a constellation can vary depending on the size and shape of the constellation.
Fill
You have not provided the dimensions of the cinder blocks. 8 by 8 by 16 in what units of measurement?
Many shapes can make up a heptagon, as long as there are always seven sides. (They do not have to be of equal length.)