1) In your merchant panel at Campaigns > Campaigns manager > click 'edit' (pencil icon) next to the desired campaign and then in the "Edit campaign" window in the top-left corner under the campaign name you will see the Campaign ID:
2) In your merchant panel at Campaigns > Campaigns manager > click "Edit view" above the grid listing the campaigns. Change the name of the new view you wish to have, check the checkbox for ID and save the view as new view. Afterwards you will see new column with IDs of the campaigns.