This option is not available in CORE Generator 12.1.
The View Resource Utilization feature from the CORE Generator tool presented numbers that were of questionable value since they did not represent how the IP core was actually being used in a design.
The Resource Utilization values output from the MAP process are more accurate and should be used.
If you want to obtain the information for an individual IP core, you can run NGDBUILD and MAP on the core netlist.
ngdbuild.exe -intstyle silent -dd .\tmp\_cg .\my_core.ngc .\tmp\_cg\my_core.ngd map.exe -intstyle silent -u ".\tmp\_cg\my_core.ngd" -o ".\tmp\_cg\my_core.ncd"