Flipping object horizontally makes face opposite

[GameMaster4268 (Game)]

In Blender, when I flip an object horizontally, the face becomes the opposite in Roblox Studio but not in Blender. Flipping horizontally means pressing Ctrl-M.

Blender:

Roblox Studio:

How can I fix this?

[GameMaster4268 (Game)]

So I exported the mesh with .obj and it worked fine but doesn’t add bones to it. I need to export it with bones without it making my objects see through.

[GamEditoPro]

1. Select transformed mesh
2. Press Ctrl + A
3. Select “all transforms”
4. Go to mesh edit workspace
5. Press A
6. Press Shift + N

Now your mesh should be fixed.