Kindly refer to the below on how to check your userID in respective devices:
iOS Device:
Tap the Menu on top left corner > Go to My Account > Device Name:
Android Device:
Tap the Menu on top left corner > Select "My Account" > Tap Device
Mac Device:
Tap the Menu on the top left corner > Select "About us"
Then, double click the Master Logo and the userID will be copied
Window Device:
Tap the Menu on the side bar > Select "Setting"
Then, select "General Setting"
Double click on the version wording and the userID will appear