If you want to get point coordinates in AutoCAD, it is easier to use the curve/polyline profil that you draw as a vector.

If you don't have access anymore to your polylines in AutoCAD, you will need to vetorize your images. Vectorization refers to the transformation of a raster image to a vector image. It can be done manually or automatically. Some vector-images softwares like Illustrator, or its free alternative Inkscape can automatically vectorize images. Once the image is vectorized, you can measure y coordinates, and reference them manually in a table.

OR if you want to automate all these operations, you can use a data analysis tool, like R / Rstudio. It can convert jpeg images to curve coordinates. https://www.r-bloggers.com/2019/06/extracting-the-data-from-static-images-of-graphs-with-magick/