C is a language that currently is not widely used. C++ is a language that is used a lot and it has a lot more cababilities than C. However, it is a big language and it is considered more difficult than C.
There's no bad thing in going into C before C++. You will basically learn a lot(and I mean a lot) of useful things that not only apply in C++ but in other languages as well. However, it is not a language that can offer you many job oppotunities and also it is a difficult language to develop any application other than terminal, command-line applications or very low-level applications(like programming drivers) but you can program that kind of applications very effectively and without the need to learn a big language. C will also help you have a better understanding about memory, but this is something that C++ can do also. C++ on the other hand can help you develop pretty much anything. From server applications to phone applications. It is much more rich than C.
It is not necessary to learn C before C++ and if your goal is to learn C++ and don't want to spend anytime in other languages, then you can as well do so. C++ is based on ideas from C, and motorcycles are based on ideas of bikes. However, you don't have to know how to ride a bike to learn how to ride a motorcycle, the same way you don't have to learn C to understand everything that you will ever need in C++. You can understand them without C as well. Personally, I had as my goal to learn C++, but decided to learn C first because of the educational things that provides and for its bautiful abruptness and power included in such a small language.
Hoped it helped. If you become more specific in what you want, maybe I can help more! :)