Though it might depends on the type of keyboard you are using... Did you try the hyphen key(the one next to "0")? --addition-- Let me explain just in case some people may confused. Japanese "ー" in katakana and hyphen or dash or minus sign looks similar but different. But the key for ー is allocated on the hyphen/dash/minus key (at least on my keyboard). Set your PC in Japanese IME(or whatever Japanese writing software) mode, hit hyphen key and then space key to convert.

These Japanese characters indicate a translation from foreign language. We call it 外來語, the Japanese scholars call it "loanword", it has to be written this way to distinquish the difference between Japanese word and loanword. "ボーイフレンド " is a loanword from English "boy friend". In Japanese, it is 彼氏 pronounce かれし. Addition: key in " boifurendo" follow by "-" key. It is a minus sign on your keyboard, you will get it translated into ボーイフレンド.