Hi Sada S

You can look this up the Surface Area of a Regular Triangular Pyramid and a Regular Tetrahedron to determine which formulas apply

For your Regular Triangular Pyramid which has base edges of length 30 and height 10

A Regular Triangular Pyramid has an Equilateral Triangle as its base and Three Isosceles Triangles as its other faces

Try

SA = Base Area + Area of its lateral faces

l = base length edge = 30

h = height = 10 is this your slant height

What are the units of your lengths

The base of your pyramid is an equilateral triangle with base edges of length 30, and the following should apply the area of of an Equilateral Triangle would be your Base Area or (√3/4)*30^{2}