Ouch! Not the best images but I think I see enough to know you have nothing left on the pads the tan area is the bare board not the copper pads which is why solder won’t stick.
Here’s a better view of the area
[image|2309721]
Apple as far as I know never offered schematics or board views of the Mac Mini series. So finding another location to tap will be difficult without having a reference board which at that point you might as well just replace the logic board. Here’s one source for the replacement logic board [https://www.thebookyard.com/parts-mac-mini-intel.php?cPath=96_217&sort=2a&filter_id=12|TheBookYard UK - Early/Late 2009 Mac Mini Logic Boards]