Add a models as one mesh

[tinwath2019 (MissYves)]

So I have a blender model that is joined and each join has a different texture, here is an example:

The thing is that when I import to roblox the textures mesh up.
Ive tried a lot of things but I dont know how to just make one texture for this. Ive saw some tutorials saying u have to bake the textures, is that the only solution? Or there are more?

[randomperson12331]

Bake the textures or separate all the segments with key L in edit mode and import them individually.