Hewbo Video Converter will help you convert MKV to 3GP with great quality, very easy to use.
Step 1: Download Hewbo Video Converter and install it.
Download links: Hewbo Video Converter for Windows, Hewbo Video Converter for Mac OSX.
Step 2: Add MKV Video file.
Run Hewbo Video Converter, Click "Add File" to load your MKV video file.

Step 3: Choose Profile.
Click Profile drop-down button to choose "3GP" as your output format.

Step 4: Start to convert MKV to 3GP.
Click "Convert" button to start the MKV to 3GP conversion.
Step 5: AVI to MP4 conversion completed.
When conversion is finished. You can enjoy 3GP videos in your PC and mobile devices now!
Is it pretty simple and easy to use? try this at MKV to 3GP immediately.