BNB needed for swap/transfer?

hello. i was sent a coin i dont usually use called 4WMM. im trying to transfer it to btc or eth but am having trouble. each time i attempt to sendd or transfer, im notified i need BNB to make a transaction on BNB network. i dont see a waty to purchase BNB on coinbase. where do i get it and how do i transfer it? thanks in advance