Triangulation algorithm for an arbitary amount of points?
In general, without additional information, you can't, due to scale ambiguity; for example, you can't tell the difference between a 1" bird that's 10' away, vs a 2" bird that's 20' away.  See, e.g., Using Headpose Vector and 2D Points to Compute Distances, calculting distance between a person and the object in the image, Is it possible to transfer a point from one camera to another, given n corresponding points?, find the actual size of an object from pixel coordinates.

If you don't have additional information but want to do the best you can, there are some heuristics; see Algorithms to convert 2D videos to 3D ones.

If you know the camera's instrinsic parameters, or the positions of the cameras, or other extra information, this is solvable  Relevant technology:


object detection lets you find the 2D coordinates of an object feature in a 2D image (you can apply this to each 2D image)
algorithms for the correspondence problem let you match these points between multiple 2D images, even without first doing object detection
camera calibration lets you figure out the camera parameters


See also Fundamental and essential matrices, value of intrinsic parameters, How to obtain the camera extrinsic matrix without using chessboard.