The hard way:
Using Granular Backup and Restore from Site Administration, choose the Blog:
http://mysites/personal/
Backup to local drive:
\\
Created a site named Blog, of type Blog.
e.g. http://sharepointsite/MyNewBlog
Use powershell to run this command in the Application Server:
Start > All Programs > Microsoft SharePoint 2010 Products > SharePoint 2010 Management Shell
Import-SPWeb -identity http://sharepointsite/MyNewBlog -path \\
The easy way:
or use the shortcut to save Blog site as template
_layouts/savetmpl.aspx
And then upload the site to the solutions gallery and activate it.
Create site from template.