Imported model as .fbx and exported to .ply, but UV (or s and t) coordinates are 0 and 1 respectively. Additionally, a texture map is required

I have a model (which I received, not created myself) in .fbx format and I want to export it to .ply format, with vertex color and UVs. Additionally, I want the texture as a texture map in .bmp or .png format.
At first, the .ply did not have RGBA, I believe this is because the color is also within the texture. So, I had to bake the texture to vertex colors. To do that, I followed this tutorial, hopefully, it is the right procedure.
My problem now is that the s and t (UV) coordinates are 0 and 1 respectively, but it should be a value from 0 to 1. I would like to know how I can resolve this and if this is possible at all using a model in .fbx format.
For the texture map, I currently just exported it to .png from the UV editor, but I’m not sure if that is going to result in what I need. Because from what I can see in Blender, there are three UV maps, see below.

I have no experience with Blender and I’m also not familiar with the file formats, so it would be very helpful if you could explain what I can do in full detail.

Below is what the very first part of my .ply file looks like.

ply
format ascii 1.0
comment Created by Blender 3.0.0 – www.blender.org
element vertex 87178
property float x
property float y
property float z
property float nx
property float ny
property float nz
property float s
property float t
property uchar red
property uchar green
property uchar blue
property uchar alpha
element face 181787
property list uchar uint vertex_indices
end_header
-1.272832 -1.550571 2.906343 -0.053774 0.668325 0.741905 0.000000 1.000000 225 155 54 255
-1.272832 -1.550571 2.902833 0.685080 0.724967 0.070986 0.000000 1.000000 225 155 54 255
-1.272972 -1.479452 2.540328 -0.101413 0.715964 -0.690695 0.000000 1.000000 225 155 54 255
…