Good morning. We are going to talk about this character 个.
个is a general measure word. It is used for nouns that don't require specific measure word. In Chinese language, most nouns are matched with specific measure words. Such as, 一张纸， 一朵花.
For some nouns, specific measure word are not required. Then we can use 个. For example, 一个人 一个苹果 etc.
Here I want to spend some time to talk about how to use 个 when we describe a period of time. You will find that for some time words 个 must be used. While for some others, if you add 个, you are making mistakes.
one hour ：一个小时 and 一小时 both are correct
two days: 两天 correct, 两个天 incorrect
three weeks: 三星期 and 三个星期 both are correct
four months: 四个月 correct 四月 means April
five years: 五年 correct 五个年 incorrect