HELP Converting a 3 view into a 3D image Cars I have drawn

I am trying to teach an old dog (me) new tricks , at 80 I am trying to convert the designs I drew some years ago into DXF usable files for some cars I have built 1/10 scale models of each and they look constructablebut I am looking to Sketchup to learn to handle it a CAD enviroment

Hello Ian and welcome to the SketchUp Community forum.

To be clear, your existing designs are drawn on paper, correct?

Converting an image drawn on paper into a DXF file, which SketchUp Pro supports, or a DAE file, which SketchUp Make and Pro support, will typically yield less than ideal results for your purpose.

Consider scanning the paper document and saving it as a JPG image.
Then, you can easily import the images into SketchUp and scale/position them accordingly for use as visual/dimensional references in tracing.

Have a look at these tutorial examples in the 3D Warehouse.

X-15 • Construction • 3-View by TaffGoch

Car Modeling Tutorial by Rouge

If you like reading books, one of the chapters in this one shows how to model a car from the kinds of views that Geo showed: