Find the lateral area and volume of the right triangular prism. side lengths are 3,4,5 and height is 6.How do I find out the apothem?

There is no apothem. Only regular polygons have one.

In this case, the lateral area is the three faces of dimensions 3x6, 4x6, 5x6

The volume is v=Bh where B is the area of the base, 1/2 (3)(4)