You can do this all on your iPad. No need to go offloading the file elsewhere.
Open up iMovie on your iPad. It should show you all the videos you've taken. If its the first time you've opened it there will be some walkthrough screens.
Next select Projects (top middle). Tap + to start a new movie. Tap movie. Tap Create (top right). Read the top of the screen, which will tell you to tap the film and music note icon. Do that. Find your video, tap it. Tap on the down arrow.
Now your video is in the bottom half of the screen. Touch and hold on the video, this will bring up something at the bottom of your screen. Bottom middle is a speaker icon, tap that, tap detach. That drops your audio into a bar below the video, tap it. Tap delete.
Hit the back arrow at top left. This will show you a screen with "MY MOVIE". Below that is 3 icons, play, a box with an up arrow, and a trash can. Hit the box with the up arrow. That brings up a thing from the bottom. Bottom left of what was brought up is 'Save Video'. Tap that. Choose size. Now your video with no sound is in your Photo Library.
I just did this, on the fly, my first time ever and I wrote instructions as I did it. I'm sure it is explained much more eloquently by other people in various other places on the web. If you can't figure it out by my instructions, check out youtube. I'd try searching "remove sound with iMovie in iOS" or something similar.