Hi Kaveh,
The link between /SAPSLL/PREVDH and the product master is the GUID_PR field.
You can get the GUID_PR by entering the product number in the PRVSY field of table /SAPSLL/PNTPR in SE16.
Once you have the GUID_PR you can then enter it into /SAPSLL/PREVDH and check the number of entries.
There is no direct link between /SAPSLL/PREVDI and the product master but you can link through /SAPSLL/PREVDH using the GUID_PREVDH field.
PNTPR -> (GUID_PR) -> PREVDH -> (GUID_PREVDH) -> PREVDI
Best Regards,
Eoin