You should be able to just cancel the recurring payments only at PayPal without cancelling the entire subscription. There's no way to do this from CBSubs without cancelling the entire subscription.
Always starts with "I-"... So I was looking for something like this in CB Subs in order to locate the person's subcription ID on CB so I can cancel it on Paypal but I can't see anywhere in CB somethink that looks like I-8RY3K797PYR.
That information is typically kept internally so you probably won't find it anywhere except maybe CBSubs > Payments if it's logged as part of the payment. Only other options would be to check the notifications for their payment in CBSubs > Notifications or check _cbsubs_payment_baskets database directly for the subscr_id.