Required reports for Dolce DC26 20” rims – Request for help

Hello guys, I bought the Cadillac CTS 3.2 (BJ. 2004) a few months ago. As a treat I had received the above-mentioned rims. Unfortunately, neither a strength nor a part report was included. A part report does not give my knowledge for my car either. However, since I do not want to drive the rims illegally, I need a strength report to have it registered with the TÜV. Can someone help me get one? Who knows how expensive such a single acceptance with Festigke please not arbitrary estimates, but facts based figures. Thank you