How do I get The C1 Label for Mavic 3 I am in the US but Travel to the UK and EU with my Drone.

Hi there. Thank you for reaching out. Users from around the world can fly in Europe, Liechtenstein, Norway, and Iceland without C1 certification until the end of 2023. If any user from outside the EU, Liechtenstein, Norway, and Iceland updates their firmware to C1-standard while being in one of those countries, the changes will be reversed when they travel back to their home country.

You'll have to apply once you arrive in EU.    They currently dont allow applications outside of the EU region.