Not sure whether to classify the following think tank publication as a journal article or report

AshLawtonD · November 14, 2021

I am not sure if the below should be classified as a journal article or a report. It seems to be academically written and appears to have an issue number.
The citation system I am using is Chicago (notes).

How should I classify it and how should I write it out?

Thanks!

Europe Programme Paper 2011/01
Perspectives on the UK’s Place in the World
https://www.chathamhouse.org/sites/default/files/public/Research/Europe/1211pp_harvey.pdf

bwiernik · November 14, 2021

I would suggest Report, putting the issue information in the series number (collection-number) field like this: https://www.zotero.org/groups/2205533/test_items_library/collections/MR2N872S/items/VP6L2CX2/item-details