Definition:
The number of cubic units to exactly fill a triangular
prism

Try this
Change the height and dimensions of the triangular prism by dragging the orange dots. Note how the volume is calculated.

How to find the volume of a triangular prism

Recall that a
prism
has two congruent, parallel faces called the bases of the prism.
The volume of any prism can be found by multiplying the area of one of the bases by its height.
In the case of a triangular prism, each base is a triangle.

As a formula
where a is the area of one triangular end face, and h is the height.

There are various ways to find the area of the triangle, use whichever method work with what you are given. In the above animation, the three sides are given, so here you would use Heron's Formula. But any method will do - below is a list of methods:

Drag the three orange dots and note how the volume is calculated

Click "hide details", then resize the prism by dragging the three orange dots

Calculate the volume yourself

Click "show details" to check your answer

Units

Remember that the dimensions and volume will be in the same units.
So if the lengths are in centimeters for example, then the volume will be in cubic centimeters (cc).