Connect Table PRPS to EKKO

Good day!

I am a functional consultant. I am creating a specs for a customized report. I need to connect Table EKKO to PRPS. Can you give another table where I can link these tables? If there are additional tables that I can connect, please provide me one. I need to get a unique field that is common to EKKO and PRPS. Field MATNR is possible...but in our case, the MATNR for Table PRPS is always blank. Kindly help.

Thank you.