There can be no closed 3D shape with only one square and 3 triangles.
A tetrahedron has four equilateral triangles as sides
There is no 3D shape with 6 faces: 4 rectangles and 2 triangles. See the link for all forms of hexahedra.
The simplest such shape is PYRAMID.
The three-dimensional shape consisting of 4 triangles is called a pyramid, or a triangular prism.
Tetrahedron or Triangular Pyramid
A triangular pyramid.
duodecahedron is a 3D shape that has 20 triangles as it's base
a duodecahedron is one 3D shape that has triangles, and so is an icosahedron. there are others, but they have very long names
A Triangular Pyramid has 4 triangles and 1 square.