Skeletal mesh rotation x 90

I used “FPS Weapon Bundle” from Epic Games Shop. And add Ka47_X to character new hand socket.
But when i add second weapon to the back (“Military weapon dark”, Rocket_Launcher), its has different X rotation. So weapon swap(Socket from Back, to socket in Hand) become broken.

I find forum post that say “Use 3d software. rotate weapon mesh, save and import to UE”, but Blender and MeshLab cant read UASSET files. All weapon data from Epic Games Shop is UASSET files.

You can export the weapons from Unreal, click on the rightmouse button over the weapon icon on the browser, then in the opened menu go to “assets actions” then “export”.
This create a FBX, now you can edit it in any 3d program fix you axis and reimport again.

Thanx Micky, its help