It is generally impossible. The mesh is a set of 3D space coordinates of control points (vertices), faces between these vertices, normal vectors to these faces, material information, mapping coordinates. On the other hand, the .FLI is a 2D animated bitmap format - a single picture (GIF-like) is saved as the first frame, and the differences to the following pictures (deltas) are saved after that. So you have no space information there, only a 2D matrix of colored pixels.

...BUT...
There is a way to create a mesh out of a bitmap picture. The color intensity (or optionally the color index of each pixel) is used as HEIGHT information - what you get is a rectangular mesh that can be used as a landscape. The program GIF2DXF does this, but it uses GIFs, not FLIs. It works best with fractal images.

And there is another way to create vector graphics out of pictures - countour tracing. What you get is a 2D polygon graphic a la CorelDraw. CorelTrace (CorelOCR) for example does this. You can then export the shape of the traced picture as .DXF or .AI file and use it in the 2D Shaper to create 3D models. This works well with logos and other exact shapes.