Step 1: To convert file, firstly, we need to start the program.
For computers which have not had Format Factory software, we can download the software here.
Step 2: The interface of Format Factory will display the supported file formats, click Video and select 3GP.
Step 3: Output Setting window: Set output parameters of the video.
When we click Output Setting, parameters for setting videos will appear (Video Setting).
Profile folder will display setting parameters, you can select parameters such as: 176*144 H263, 352*288 H263,...
Then, click OK.
Step 4: After finishing the select for setting up, you can add files or folders to select the videos that you intend to convert.
Add file: You can add file that you intends to convert.
Add Folder: You can select folder to convert
Here, I will select Add file to convert
In Output Folder, I will default as D:\FFOutput, you can also select default output folder on your computer!
Finally, click "Click to Start" to easily convert the file to a 3GP file.
Here is your product. It is very simple, isn’t it?
It can be said that: Thanks to Format Factory, the conversion of a video file into 3GP format is very simple.
source : http://tips.betdownload.com/convert-video-into-3gp-with-format-factory-1282n.aspx