In TSR my mesh totally works fine but when I export it into ts3 the mesh becomes broken whenever I use the thin/fat sliders and the muscle sliders as well it's fine in TSR when I use the sliders there but not in ts3 help!

https://imgur.com/a/hAt4e0r

First thing, is that the mesh is way too big. Your LOD1 vertices count is almost double what the game can handle, with an L2 and L3. I try to keep it around 7k to 8k max, and heavily decimate L2 and L3. That face count is also outrageous.

Easy way to know, is when the hair explodes in TSRW. MTK, Geom Tools, Match Morphs, has a chart.

Is that an MMD or XPS conversion?

Thank you I understand now, it's a conversion from shining nikki meaning it was an fbx file

I have done a few conversions of TS4, MMD, XPS and most likely FBX. Some are such low poly that they look horrible, and I don't bother... some are so high poly that it's impossible to bring count down, and retain a good looking mesh. Some, are workable.

The main issue with garments are the morphs. I'm not sure how they fit into the vertices calculations, but I will tell you that I have a few "specialty" outfits, that do not have morphs, and are higher poly than your project.

I hope you get the count down. If not, open a thread in create section.