....but from first principles.
I feel you may be crying for the moon!
Any and every scan produces only a picture.
The image can be read by OCR and turned into text.
This is by clever software and pattern recognition.
I have "converted" an image into a vector drawing program, by tracing (laboriously) over the imported image and when a fundamentally new vector drawing is in place, the original import is deleted.
Result is a drawing which looks OK and can be further improved, but all the essential Autocad scale and dimensions would be missing.
In my mind you, without an original Autocad file ... are stuck.