Mapping handling unit IDs to material numbers

Dear Gurus,

I want to map handling unit IDs to material numbers (MATNR from /SAPAPO/MATKEY). How can I do this? Which tables do I need to join with /SCWM/ORDIM_C?

I found attribute MATID in table /SCWM/ORDIM_C which contains 32 digits and is a hex code. There's also an attribute MATID in /SAPAPO/MATKEY but this one has 22 digits and is a string.

Regards,

Mike