Each blog you create has its own unique ID number. Usually, you won't need to worry about this, but occasionally it can be useful to know this number. For instance, several third-party services you may want to install require a blog ID number. So if you ever need to figure this out, here's how:
First, sign in to Blogger. Then choose the blog whose ID you want to find, and click on its name.
From any of the posting, settings, or template pages, you can find your blog's ID number if you look at the URL in the address bar. At the end of the address, you can see that it says
blogID=XXXXXX where the X's represent your blog's ID.
Every blog on your account will have a different ID number, so make sure you get the right one.