Call Park is not supported on the 5000, so there is no feature code.
The easiest work around for "park" positions is to use hunt groups, with a phantom as the only member. Use the hunt group recall timer and destination rather than dealing with station hold, recall and attendant issues and timers.
Transfer the call to the park hunt group, and use reverse transfer to retrieve the call. Super easy if you put a hunt group key and pick-up key on the phones. Create as many hunt groups as you need, and call them Park 1, Park 2, etc. One button pushed to park the call, two buttons pushed to answer the call.