How to Move Posts From One Blog to Another on Tumblrby Ashley Poland
Tumblr doesn't have a mechanism for moving posts directly from one blog to another. However, this doesn't mean that posts cannot be moved over to one of your secondary blogs that you've created under the same email address. To move a post, you need to reblog it to the target blog. If you want to remove the original post, you can delete it when you're done.
Reblogging Your Own Post
View your posts by opening your blog at tumblr.com/blog/username -- where "username" is your blog username. This provides a dashboard view of all your posts, rather than going into your theme. Click the reblog button on the post you want to move. At the top of the reblog screen you can choose which of your secondary blogs you want to copy the post to. Once you've selected your blog, click the "Reblog Post" button.
Reblogging From the Dashboard
Just like when you're reblogging your own post you can select the target blog when you reblog another post from the dashboard. The drop-down box for selecting which blog you share to is at the top of the post in the same location. You cannot reblog to multiple blogs at the same time.
Deleting a Post
If you want to remove a post after sharing and reblogging it, you can do so from the blog view. Next to the reblog button at the top of the post is a Delete button. Tumblr will prompt you to make sure that you want to delete the post. If you want to remove multiple posts at once, you can use the mass post editor. The link to the mass post editor is on the right sidebar on your blog view.
In addition to sharing the post, you can also make changes to it when you reblog it. Adding tags can make it easier to categorize and search posts, both for your own reference and for users to find you when they using Tumblr's search system. You can also choose to add the post to your queue, schedule the time when it goes live or even set it as a private post. In 2013 Tumblr added the option to change the post type -- for instance, you can change a text post to a link or quote post.