The Curt Trailer Hitch # C38BR you purchased for your 2023 Mazda CX-50 uses (4) M12 x 1.25 x 40mm, and (4) 1/2" conical toothed washers. You can pick this up from a hardware store or with the # RHK.
I couldn't find any order history with us but you can also reach out to whomever you purchased the hitch from as all hitches should include hardware, so they should send you some. view full answer...