Cache Rules are under: Caching -> Cache Rules https://dash.cloudflare.com/?to=/:account/:zone/cachin

Cache Rules are under: Caching -> Cache Rules
https://dash.cloudflare.com/?to=/:account/:zone/caching/cache-rules/new

Easiest way to match it would be
Hostname equals cdn.fullqueuedeveloper.com

He's already got an existing Page Rule or Cache Rule for it to cache it that long. If it's a Page Rule, he should recreate it as a Cache Rule. If it's a Cache Rule, he should just modify the existing.

The exact TTL is up to you. Cloudflare caches 404s for 3 minutes by default for example.
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