To get new Sales order number,Project proposal id and Transfer order number in Ax 2012 You can get hints from below code.
//Get new sales Id
salesTable.SalesId = NumberSeq::newGetNum(SalesParameters::numRefSalesId()).num();
//Get new project proposal id
NumSeq = NumberSeq::newGetNum(NumberSeqReference::findReference(extendedTypeNum(ProjProposalId)));
//Get new Transfer order number
inventTransferTable.TransferId = InventTransferTable::numberSeq().num();
Where parameter table is used and extended data type passed in method.