If you want to convert 3GP files to VOB, you might as well try this wonderful 3GP to VOB Converter, which can easily and quickly convert 3GP, 3GPP 3G2 video to VOB with fast speed and high quality.
Aparting from converting 3GP to VOB professionally, this 3GP to VOB Converter can allow you to edit the input videos freely, like video splitter, movie cropping, adjust video effect like brightness, contrast, saturation, etc.
Download free 3GP to VOB Converter suppported. Just have a try and experience it by yourself.
After you install and run 3GP to VOB, the user-friendly interface shows as below:

Step-by-step guide on how to convert 3GP to VOB:
Step 1. Add MOV files- Click "Add files" button, usual "Open" dialog shows up. Browse to the folder where your 3GP file is, select it, click "Open". Batch 3GP to VOB conversion is supported.

Besides, you can capture the image as .jpg, .bmp, .gif format while previewing the video.
Step 2. Edit 3GP Video- Click "Effect", "Crop", "Trim" buttons seperately, 3GP files to VOB allows you to cut the video into segments, to crop the movie by reset the value, to set Effect like brightness, contrast, saturation to adjust video playing effect.

Step 3. Output settings- Choose the proper output video format as (.*vob) and set a location where output file will be saved. And if you want to join the input videos, just check "Merge into one file" option.

Step 4. Convert 3GP to VOB- after preparations, click "Start" button to begin the 3GP files to VOB conversion. Just a while, you can get the VOB files with vivid images and rich sound.

If you want to convert 3GP to VOB, I hope this Emicsoft 3GP to VOB Converter can help you and this guide on how to convert 3GP to VOB can give you a hand.