Creating a Vector File

You need to describe what you intend to do with the vector drawing. Auto-tracing is seldom the way to proceed for optimal results. For example, if your purpose is to create additional stencils, cut sign vinyl, etc. on any kind of plotter-cutter, I would not recommend auto-tracing.

There is no lossless "conversion" between raster-based graphics and vector-based graphics, in the sense of converting one file format to another. People need to stop using the term "conversion" in this content, because it is grossly misleading.

Whether automated by an auto-tracing feature or not, it's still a process of completely re-drawing the image as vector paths; creating an entirely other version of the image using a different digital medium. So auto-tracing is just as subject to entropy as any other mechanical reproduction process; degradation occurs in each generation of copying.

JET

Could you show one of the stencils, so appropriate advice can be given as to the practicalities of various options?

Image trace is the traditional way to convert raster to vector.

However, try this option:

Photo to vector converter app for iOS, Android | Adobe Capture CC

alwfineart  wrote So far, I've failed miserably (which, I guess, is to be expected, since I'm new to Illustrator).

What have you done so far that has failed?