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What you show is the USB dongle used by various magix programs to convert analogue video to digital, but we need to know which program do you use it with?
To be clear; the dongle cannot work without the Magix program that it was originally supplied with.
The activation/serial code would have been given to you at the time of purchase, most likely in the box that originally included that dongle. If you registered the purchase with Magix you might be able to find the serial code by logging into your Magix account going to "My products" and finding the listing for the program you have.