Hello,
I managed to clone the USB flash drive with a DS3622xs+ install.
I share it:
1.- I have made an image of my flash drive, with Synology installed and working, to a bin file with this program: https://www.osforensics.com/tools/write-usb-images.html
2.- Then with the program "GetFlashInfo.exe" (usbdriveinfo.zip), I have extracted the VIP and PID of the new USB. There are other ways to know the VIP and PID manually online.
3.- With OSFMount I have mounted the bin of the flash drive image with the installation of our version of sysnology. We choose partition 0 (zero), and uncheck read only.
4.- In the [x]:\boot\grub\ directory, there is a file with the name "grub.cfg".
5.- We edit the "grub.cfg" file and replace the VIP and PID with the new ones from the new flash drive. There are two.
6.- We save the changes. We disassemble the bin.
7.- We record this bin on the new USB drive.
8.- We unmount the new USB drive
9.- We tested the new drive on our NAS.
I hope it helps you all.