FrontAccounting system transaction types are listed in includes/types.inc and maps onto the labels in the Forms Setup screen. You cannot add new transaction types (except through custom or standard extension modules). Cash Payment Voucher is a type of Bank Transaction. In the said file look up: Bank transaction types:
// Bank transaction types
//
define('BT_TRANSFER', 0);
define('BT_CHEQUE', 1);
define('BT_CREDIT', 2);
define('BT_CASH', 3);
Under Banking & General Ledger tab check out the Bank Accounts screen - you will find that petty Cash is a Bank Account.
When setting up a bank account, choose it's type from the the above choices - in your case, it will be Cash account (BT_CASH => 3).
Bank and Cash Vouchers use a same numbering sequence.
Packing List and Delivery Note use another same numbering sequence.