You must have _AAA_STALKER2__2.7z.001 in the same folder. If there are more parts (e.g., .003, .004), those must also be present.
Place all numbered parts ( .001 , .002 , etc.) in the . Right-click on the first file ( _AAA_STALKER2__2.7z.001 ). _AAA_STALKER2__2.7z.002
Hover over the menu and select "Extract Files..." or "Extract Here" . You must have _AAA_STALKER2__2