I suppose that is a viable option, but I know there may be those little triangle markers that show exactly where each piece matches up with the other, although perhaps those do not exist on a machine-made garment (?) and I worry that I will not know enough about how to reassemble if those cues are missing.
Dont think you' re gonna find them, but you can always mark the pieces yourself before taking it apart.
I just get a couple of crayons in different colours and mark connecting pieces , and what ever there is " special" and make pic's.
When you trace it , just transfer your marks onto the pattern .
That is exactly how to make a garment when deconstructing to copy the pattern. Take a look at a pre-fab pattern to see where the "triangle things" should be and mark those spots on your dress using something that will not rub off. Transfer those marks to your pattern pieces. Cut as close to the stitching as you can and add a seam allowance. Some pieces will have been trimmed after sewing, it would be valuable to consult with somebody who has a little experience sewing to explain where that may have been done on your dress. Also, making a mock up of the dress in cheap fabric to check for fit before cutting your good fabric is advisable.
You can do it! Just give yourself some time and room to make errors (those are how you learn the most