Hello Krzysio,
The best way to do this would be to either put sockets on the static mesh at those locations and then reference their location or, in the case of a basic shape like this, you can calculate to get it.
Using local transform (or world, but be sure to offset it all by the static mesh’s world transform if you do this), you can get one of the bottom corners by plugging in half the X, half the Y, and half the Z size of the static mesh itself. This assuming that the root of this static mesh is directly in the middle.