One of the first things new learners of Japanese must struggle with is the amazing variety of classifiers for numbers. When counting books, for instance, the number is followed by 冊 (satsu, volumes, as in issatsu, nisatsu etc.); for thin, elongated objects such as pencils it's 本 (hon, as in ippon, nihon, sanbon, etc.); for pieces of paper like tickets it's 枚 (mai); for à la carte orders of sushi it's 貫 (kan); for pairs of shoes it's 足 (soku); and so on.
There's no generic counter that will cover everything, but in a pinch you can resort to the classifier 個 (ko), as in 一個 (ikko, one piece). In daily speech, 個人 (kojin) means an individual, and is heard in situations like 個人的に何の関係もないです (Kojinteki ni nan no kankei mo nai desu, I have no personal contact with [him] at all). You may recognize the sign 個人 (kojin) atop some taxis, which indicates an owner-driver.
For translators like yours truly, numbers present little difficulty. What's harder to deal with are Japanese suffixes, which don't always neatly mesh with English equivalents.