A triangle is a plane figure (two-dimensional) so has no volume, but it has an area.
There are essentially two formulae for the area: ½base×vertical height, and: the product of half the lengths of two sides and the sine of their included angle.
The volume of a triangular prism is the area of the triangle multiplied by the length of the prism.
The volume of a tetrahedron (triangular pyramid) is ⅓(area of triangular base)×vertical height. The tetrahedron has 4 triangular faces.
The volume of a pyramid with base which is a polygon (more than 3 sides) is the ⅓(area of the polygonal base)×vertical height. Apart from the base, all the faces are triangular.