Can I get this Mavlink ID for Unknown(mission command)

Ground Control Software Mission Planner
1

I want get Mavlink ID for Unknown.
I use quadcopter.

Unknown
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2

You can save the mission item list as a file and look at the 4th column of individual rows. E.g. 16 is for a waypoint.
https://mavlink.io/en/messages/common.html#mav_commands