How can I type 吗 in Pinyin keyboard setup?
As you are using the "Pinyin - Traditional" input method, maybe what you can see will only be the traditional character "嗎". To convert it into simplified Chinese, try this tool by pasting it into the blank and click the second button.

By the way, sometimes we also use "麼" (or "么" in simplified form) at the end of a question. And the corresponding Pinyin should be "me", although most Chinese may pronounce it as "mo".