Number + 月份
十月份 (shíyuèfèn) means "October" or "the month of October." Adding 份 (fèn) after a month name is optional and adds a slightly more colloquial or emphatic tone, specifying "the month of" rather than just naming the month. Both 十月 and 十月份 are correct; the 份 suffix is commonly used in spoken Chinese and news writing.
十月份的天气已经开始变凉了。
Shí yuèfèn de tiānqì yǐjīng kāishǐ biàn liáng le.
The weather in October has already started to turn cool.
我们打算十月份去日本看红叶。
Wǒmen dǎsuàn shí yuèfèn qù Rìběn kàn hóngyè.
We plan to go to Japan in October to see the autumn leaves.
公司计划在十月份推出新产品。
Gōngsī jìhuà zài shí yuèfèn tuīchū xīn chǎnpǐn.
The company plans to launch a new product in October.