Hi Kanu Pathak,
You can use DTW add on to transfer bill of material in SAP Business one.
The required DTW templates are OITT and ITT1 templates which can be accessed from the path,
C:\Program Files (x86)\SAP\Data Transfer Workbench\Templates\Samples\1. Add New Data\Production\Bill of Materials
Hope helpful.
Thanks & Regards,
Nagarajan