What is the surface forms a triangle square circle?

im making a birdhouse for prodject load and you must find the area of the bird house so I need the formulas for area and instead of Triange ….. circle and that someone could give me instructions step by step on how to find it. SORRY! please and thank you

Circle = Pi x Rsq. Triangle = B x H / 2 = square wxh

Math Calculations & Conversions : How to Calculate the Circumference of a Circle