Amazon MTurk funds are used to pay workers for studies run on MTurk using your MTurk Requester account (through the TurkPrime website or directly through MTurk)
TurkPrime Lab balance can be used for:
1. Full Lab Service: Prime Panel Studies https://www.turkprime.com/Service/PrimePanels
2. Full Lab Service: MTurk Panel Studies
3. MTurk Toolkit: TurkPrime Pro feature
4. MTurk Toolkit: MTurk Panels (NEW)
Since MTurk and TurkPrime are managed by two independent companies there is no way to transfer funds from one account to the other.