how to install specific version of Ruby in Arch-Based Linux

I was trying to install specific version Ruby in Manjaro. I had tried some query.

sudo pacman -Sy ruby:2.6.6
sudo pacman -Sy ruby-2.6.6

Both of them returning target not found. I was reading the thread. But, Some people said that pacman doesn't allow to install specific version. How can I install specific version of Ruby then? Current Ruby version is 3.0.1. But, I need 2.6.6. So, I must have to install that version of Ruby.

I had installed 2.6.6 following way.

sudo rvm install 2.6.6

When I tried to use it

sudo rvm use 2.6.6
sudo rvm use 2.6.6 --default

I got following error

RVM used your Gemfile for selecting Ruby, it is all fine - Heroku does that too, you can ignore these warnings with 'rvm rvmrc warning ignore /home/istiak/qpixel/Gemfile'. To ignore the warning for all files run 'rvm rvmrc warning ignore allGemfiles'.
RVM is not a function, selecting rubies with 'rvm use ...' will not work.You need to change your terminal emulator preferences to allow login shell. Sometimes it is required to use /bin/bash --login as the command. Please visit https://rvm.io/integration/gnome-terminal/ for an example.