My Late 2012 iMac (27") is supposed to have Thunderbolt ports but Thunderbolt cables will not fit

My Late 2012 iMac (27") is supposed to have Thunderbolt ports but Thunderbolt cables will not fit. Port is just a hair too small (short). I need a cable that connects this old computer as a display to my 2019 iMac (also 27") but can't find one.

The 2012 Thunderbolt ports (both of them) appear to have 10 pins in a straight line. However, all research I've done shows 9 pins in two rows.

Am I out of luck? Any other connection solutions so old mac can become a display for new mac? Thanks in advance!