if so where can I find it ?

I don't believe there is one. Any information on the 300ER is towards the back of the 200LR manual.

IIRC, manuals under the Boeing License cannot be bundled. They were/are available to buy at PMDG. And very expensive too.

if so where can I find it ?

The manuals include all B-777 variants, and where differences exist between them it is identified in each paragraph or in tables (as in limitations).

 

Or, are you asking where were the manuals installed on your systems?  See Start Menu PMDG Operations Center, select the product and then select documents on the menu.