where can I find a 3D worm model to put in blender. not the model from worms 3D or worms forts I'm talking about a model from worms 4. please help me

Blender? Never heard of that...

I assume you have the game? Then you find the .xom file in c*\Worms 4 Mayhem\data\Character\w4worm.xom

Is that what you are searching for?

*whereever you installed it

Blender? Never heard of that...
It's a well-known free 3D modelling program.

The worm model is definitely a separate file, and it's probably the one Thurbo said, but I'm pretty sure Blender can't open the .xom models. It's possible though, it's been done before, so if Blender won't open it by itself try searching the forum for an answer.