[Mateo]

It seems that you need a "010 -- m2blptemplate. bt" template

Where can I find this template? Or is there another way?

[Atraxian]

If what you are asking is how to change the path of hardcoded textures in models, it is relatively simple.

This is for models for 3.3.5a.
I use 010 editor with Alastor's template (link at the end)

ALWAYS MAKE A BACKUP OF THE MMODEL BEFORE STARTING. I know it's basic stuff, but you don't want to skip this, trust me.

Just load the .m2 model with 010, run the template on the file and look at the result. You will find a section named "struct Textures"

there you can open the textures you want to change:

An important part is the enum E_TEXTURETYPES type value.
Depending on it you can make the testure hardcoded (you have to specify the path inside of the model itsel) or being automatically taken fromexternal sources.
For example monsters with multiple textures variations have MONSTER_SKIN_1, 2 and/or 3. These textures are taken from the Monster Texture Variation columns in the CreatureDisplayInfo.dbc

I'm assuming you want to hardocde a texture or change the path of a hardcoded texture, so let's start with that.

Click on the "string texture[xx]", you will notice that the upper part of the editor automatically went to the values of the texture path:

You can change the texture path by rewriting the part on the right hand side, but you have to be EXTREMELY CAREFUL about two things:
1) the length of the path
2) the starting position of whatever comes after the texture

Let's start with point 1: after you write in the new texture path, count the number of characters and input that number into the FileName_length section. Simple enough, right?
Point 2 has 2 cases:

 SHORTER PATH THAN THE ORIGINAL
fill in the path, then click on the hexadecimal part of the editor and start hitting 0 until you restore the next texture to its original position

This is because the structure of the file has many many MANY points where it looks up the exact position of informations by using hardcoded offsets. If you change the length of something you run the risk of shifting everything and make the model unusable.

LONGER PATH THAN THE ORIGINAL or NEW HARDCODED TEXTURE
in this case you don't have enough room in this part of the file than before, but that's where the offset become your friends. You just have to insert the texture path at the end of the file and put the appropriate offset so the model knows where to look for it.
First, go to the end of the file and fill in 0 until you start a new row, then put in the new texture path

right click on the template result section and select column display format as hex, like this:

now change the FileName_offset of your texture to the value on the left had side of the hex editor at the start of yout path row. In the example case it is 2D19C0h
Return to showing things as Default or Decimal and change FileName_length to the appropriate number.

This way you should have been able to hardcode or change a hardcoded texture with the 010 editor without going crazy.

for reference:
https://wowdev.wiki/M2#Textures 

for the template: