<p>Does anyone know of a good way to convert a 3D print file, like STL, to STEP - a useable file format for plastic injection molding companies?  </p>

<p>I have tried to convert the files through a couple of programs without success. The most requested file is a STP or STEP file.  If there’s no easy way to convert it, which I don’t think there is, does anyone know someone good at re-creating CAD files?</p>

I've been able to manipulate an STL file using the hobbyist version (free) of Fusion 360. There's a series of steps involved that may require some research and experimentation, at least it did in my case.
One loads the STL file into Fusion 360 by using Insert, Mesh.
Once loaded, turn off history.
The next step is to
convert the mesh file to BREP
.
In that form, the surfaces can be edited and the model can be modified if necessary.
I have not exported to STEP, but have confirmed that
Fusion 360 supports STEP
as a valid export file format.
Both links provide additional information that may be of value to your project.
Consider also to double check your STL file to ensure it is manifold.
Meshmixer
is useful for such purposes. One model imported into Fusion 360 had entire faces removed due to a manifold error in the original model.