Put Noindex Tag on Subdomains

Hell guys, hope y'all are well. I've a question regarding noindex tags on subdomains. My client has a lot of subdomains that Google crawled but he wants me to put noindex tags to them. Those subdomains are his past projects and portfolios of his freelancers but unfortunately, Google crawled them and it's on the "indexed pages" on GSC. I can't find those subdomains on his website. How can I put noindex tag to those subdomains that are not on his website?