If you want to scan chips or anything else 3D buy an HP.
Canon & Epson both stink for 3D unless you want to put a colored background in or crop out circles every time.
250dpi is not a 'standard'
You may only be able to save your settings using one of their predefined resolutions which I think are 75, 100, 150, 200, 300.
I bought an Epson a couple of weeks ago - took it back the next day and paid the $30 extra for the HP.
Ive had Canon before - if its advertised as a document scanner then thats what it is - documents not 3D. If you call Canon and tell them what you are trying to do they will recommend a $3000 model

You can turn the 'auto numbering/saving' feature off. I got that far before returning it

Use Photoshop