I have a fan page and would like to change it into a group without losing my fans and retaining my videos and pictures.
Is it possible to transform a Facebook fan page into a group?
It's not possible to convert a page into a group or the reverse. Below is the quote from the Group -> Page help on Facebook and gives good advice on how to do it manually.
According to this Facebook Help
It is currently not possible to convert Facebook groups into Pages. We recommend that you create a Page and notify your group members about it. Note that you will not be able to send your group a message if your group has more than 5,000 members.