The first thing you need to do is to login into your Blogger dashboard through your Google Account. After logging in, from the list of your blogs under your account, select any one blog. It depends on you whether you click over its name or open any other area of the same blog.
blogID=XXXXXXXXXXXXXXXXXXX where the "X's" represents your Blog's ID. For more detailed instructions, check out the following screenshot.
Note: Every blog that you have on your account consists of different ID numbers, so be sure that you are getting the right one. The Number ID consists of 19 digest code, so before you use them make sure that you are copying the right numbers in the correct pattern.
We hope this article has helped you in learning How to Find Your Blog's Secret ID Number in Blogger. In the coming tutorials ahead, we will be showing you some ways through which you can use this ID Number to install some third-party Plugins for your blog. Keep in mind that, these are the secrete numbers which can only be seen by either Blog authors or administrators. Take extreme precautions while using them. If you have any confusion, try commenting below.