Q: i want to transfer video from my iPad to my imac

Several options depending on age of devices:

1. You could use AirDrop if the Devices support it:

     How to use AirDrop with your iPhone, iPad, or iPod touch - Apple Support

2. You could use a transfer App such as Transfer Lite

https://itunes.apple.com/us/app/photo-transfer-app-lite-easily/id490425032?mt=8

3. If the Videos were taken with the iPad and reside in the Photos App on the iPad, you can Import them using Photos or Image capture on your Mac

Import photos and videos from your iPhone, iPad, or iPod touch - Apple Support