How to find and change texture paths for .mdl?

[StormyG7]

I never messed with models, only simple texture edits or icon edits. I have a bunch of .mdl files and texture files in .dds, .plt, and .tga from another game. The problem is I don't know why the textures won't appear on the model. Is there a program or tool I can use to change texture paths on any .mdl?