If you were previously using WordPress.ORG for your site(hosted somewhere else), then you can migrate you entire site from WordPress.ORG to WordPress.COM by following the instructions given here:
More moving options can be found here:
If you need help from the staff in migrating your site you can reach them by tagging this question with the modlook tag on the Tags section of the sidebar.
Read about the modlook tag here: https://en.support.wordpress.com/getting-help-in-the-forums/#how-do-i-get-a-moderatorstaff-reply-for-my-question
You can also subscribe to this topic by clicking on the "Subscribe to Topic" link on the sidebar to get email notifications whenever someone posts an answer to this thread.
NOTE: You will have to contact the individual who previously developed the site for your hosts login details, if you cannot contact him/her then please contact the support team of your host. You will need the login information because you will have to export the contents of your site from your dashboard.
Hope this helps! 🙂