Your PSP must be running Custom Firmware (CFW) such as PRO-C or LME.
This source offers a download link for a "Call of Duty Black Ops PPSSPP ISO" clocking in at 890MB. The blog lists extremely high system requirements (35000 mAh battery, 1440p displays) that are technically inaccurate or exaggerated, raising red flags about the file's authenticity. call of duty black ops psp iso download verified hit
Before downloading, ensure your PSP meets the system requirements: Your PSP must be running Custom Firmware (CFW)