Need help exporting a pose

I try since some hours now to export a pose from a model in fbx format.
Exporting the pose as obj works but all skinning is lost through obj.

I tried this:

Select the mesh.
Press alt + c .
Select 'Mesh from curve/meta/surf/text'.
Click 'File' -> 'Export'.

what is mesh in this? wich mesh should be selected? Tried every component in the scene collection.
Pressed alt + c --> nothing happens.

then I tried to Convert object to mesh:

  1. Select the curve object you’d like to convert to a mesh.
    2. Go into Edit mode.
    3.In the Edit buttons, you’ll find a slider (in the Curve Tools tab) saying “Resol U”. Change that to a lower value.
  2. Convert to mesh.

What are edit Buttons? Google don’t giving me pictures of something clearly

Then i tried to apply my pose as rest pose, but the model (bird) get deformed and unusable.