If you don't know why you must do this asap, please read this.
There is free software that will handle the migration for you.
This migrates the content of your site to the newer version, but there are complications.
Each site is unique and the degree of difficulty will vary considerably.
You may be able to do the migration yourself, or you may need us or another developer to help.
We're offering to analyse your site for free. We'll give you our honest opinion about how you should proceed and it is then up to you what you do.