As a (now ex-) Software Team Lead, this is a quick rant about putting the phrase 'C/C++' on your C.V./resume, based on my experiences of recruiting over the past couple of years.

TL:DW - When applying for a C++ role, if you put 'C/C++' on your CV and you are a C++ programmer you are selling yourself short.  If you put 'C/C++' on your CV and you don't know idiomatic C++ you are wasting everyone's time.  Better to be upfront about it and focus on selling your other skills.

Some decent C++ books/resources that I've personally bought and read (were originally affiliate links but not any longer):
Scott Meyers - Effective C++ (there are more in the series)
https://amzn.to/2EhKFFL

Herb Sutter - Exceptional C++
https://amzn.to/2YVnPgr

'Gang of Four' - Design Patterns: Elements of Re-usable Object-Oriented Software
https://amzn.to/38GaVYf

Stack Exchange discussion about the differences between C and C++
https://softwareengineering.stackexchange.com/questions/38942/how-is-c-different-from-c