So I have a mac computer but i plugged in a windows keyboard in my mac. I am still trying to figure out how to paste commands into a command block. So how can I paste a command?
This actually depends on what version you're using. Since there's no right-click function in the command block menu, you have to use keyboard shortcuts; however, different versions use different shortcuts. Minecraft 1.7.10 and earlier were all made using the shortcuts for Windows and other systems, so if you're using one of those older versions you have to use Ctrl+V to paste. This gets confusing, because other applications still use ⌘ on Mac. However, if you're using any version of 1.8 or later, you can use ⌘ + V, like the other applications on Mac do.
TL;DR ⌘ + V if you're using 1.8 or higher, Ctrl+V if you're on 1.7.10 or lower