Back up your files and databases. Then follow the instructions here:
http://b2evolution.net/downloads/index.html

Thank you for your feedback,

However, While doing backup. I am getting below error message. And could you please tell me how long it will take to backup the contents. I have 50 posts only. I am using this blog since 4 months.

Unable to create «/home/content/58/10667258/html/_backup/2013-08-28-07-01-17/files.zip»

Switching out of maintenance mode...

Thanks,

Thank you for your feedback,

However, While doing backup. I am getting below error message. And could you please tell me how long it will take to backup the contents. I have 50 posts only. I am using this blog since 4 months.

Unable to create «/home/content/58/10667258/html/_backup/2013-08-28-07-01-17/files.zip»

Switching out of maintenance mode...

Thanks,