The contents of the community.db were merged into extra.db two years ago, and this was announced on one of the Stable Updates threads. This meant that from that moment on, community.db was empty, even though it still existed (without any content) on the mirrors.
About two months ago, community.db was removed from the mirrors, following the decision of Arch upstream to do the same with their own previously merged community.db. This too was announced on a Stable Updates thread.
As the quick & dirty solution to your problem, you should remove the following three lines from /etc/pacman.conf… 
[community]
SigLevel = PackageRequired
Include = /etc/pacman.d/mirrorlist
However, the fact that you are running into this problem now suggests that you have not been maintaining your system. The change regarding community.db was reflected in a .pacnew file, and you are now running into this problem because you have not been merging your .pacnew files.
.pacnew files must not be ignored, nor must they be blindly copied over your existing configuration files. They are sample configuration files reflecting technical changes upstream, and they are meant to be merged with your existing configuration files.
You probably have loads of .pacnew files on your system by now. You can check this with the command…
pacdiff -o
If you do not have that command at your disposal, then you must first install the package pacman-contrib.
Lastly, Manjaro is not a set-and-forget distribution. As a (curated) rolling-release distribution, it requires being kept up-to-date, as well as periodic hands-on maintenance, as explained in the essay below…
Further reading regarding the community.db issue…
Edit:
I had not seen this yet. I am going to close and unlist the other thread, given that it serves no purpose anymore and that the formatting of the terminal output is just plain horrible and makes it unreadable.
@a2apple, only one thread per issue, and one issue per thread. Please see the Forum Rules.