anyone online ?? i need help urgently

Short of someone recording hours of video of how they'd build this part, your question can't really be answered.

This is a pretty advanced part. Do you have a lot of experience with NX? You have no models loaded under your profile, so it is impossible to gauge your experience level. I've used SOLIDWORKS for 20 years, and I'd likely need to build and rebuild this model 2-3 times until I was happy with the results. Each rebuild might take 6-18 hours.

The data appears to be from a scanning system. But there are many holes which can only be guessed at without additional data like reference photos.
What is the project for? How closely is the new CAD data supposed to match the STL file?

As a general guide, start by mentally splitting this model into smaller chunks which you can begin modeling. The mounting tabs, circular and semi-circular bosses can all be built. They may not be the best place to start this model, but at least it is a starting point, and people will see you've put some effort into the model, and also be able to judge your level of competence with the software.
The STL file can be useful as a reference while building the model, but it is going to require a lot of time and skill to create a good CAD model.

Another starting point is laying out all the boundary edges of the model. This will be a lot easier since the scan data can be used as a reference, but it is not going to be easy. Lots of 3D curves and splines are needed. If those are made poorly, or in the wrong spots, the rest of the model will never be correct.

Become very familiar with the Reverse Engineering tool-set. Fit surface is going to be used a lot to reconstruct this and of course, the million dollar question... to what degree of deviation?
Short answer: create necessary fit surface slabs and trim to get general shape and then the work is just beginning as this is a very busy model. But if you can't flesh out the general shape... you're probably in over your head until you learn more surfacing tools/techniques.

And... I second getting a better scan.