command line – AUR Package Problems

I dont know whether this is the best place to ask but, ive recently installed xubuntu and im trying to make my desktop look like macOS, im following a tutorial where they download AUR packages, how do i access this and install packages, i have tried to download through the git clone, however when i enter makepkg -si, it comes up with “makepkg – command not found”. I then tried to download the base-devel, but it then says pacman command not found. All i want to do is download the packages, is it really that hard? I do apologize as i dont know anything, but im tring to learn.

Thanks for reading, any help would be fantastic!!