Hi AED_830, I am Paulo and I'd like to help.
Since your scanner doesn't have a feeder and only a flatbed, the only way is to scan them one by one and then merge these files into one PDF file using a free merger like this from Adobe
https://www.adobe.com/acrobat/online/merge-pdf....
If the scans are jpegs or images, see if this can help
https://www.adobe.com/acrobat/hub/how-to/how-to...
(Disclaimer: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.)