Hello 王虾仔,
If you purchased on Google Play Store:
Google doesn't provide a way to transfer paid apps from one account to
another.
Still, you can add your "old" account to Accounts & Sync on your
phone and select this account in the new updated
Play Store app (menu => Accounts).
If you purchased on Poweramp website:
Please just send us your new desired google account. Please send it from
your previous google account, email used for the purchase, or please
provide the order/invoice id so we can know the request actually comes
from you.
Thanks!