Raising Errors in SQL Server ( THROW Command) with IF condition - SQL Server

I am trying to update my script from the RAISERROR Command to the THROW Command. I am in a "If statement" condition and if the contidion is True return the error. For the RAISEERROR command I do not have an issue, however when I change to the THROW Command, there is no possible.

RAISERROR Command:

CREATE OR ALTER PROCEDURE Auction.uspAddProductToAuction
(@ProductID INT,@ExpireDate DATETIME = NULL,@InitialBidPrice MONEY = NULL) AS

DECLARE @IND_ADD_PRODUCT TINYINT
SET @IND_ADD_PRODUCT=1

IF ([Auction].[ufnGetStock](@ProductID)=0) --> true
BEGIN
        SET @IND_ADD_PRODUCT = 0
        RAISERROR ('The product is not in auction campaign discount or a product was not inserted',1,0)
END

THROW Command:

CREATE OR ALTER PROCEDURE Auction.uspAddProductToAuction
(@ProductID INT,@ExpireDate DATETIME = NULL,@InitialBidPrice MONEY = NULL) AS

DECLARE @IND_ADD_PRODUCT TINYINT
SET @IND_ADD_PRODUCT=1

IF ([Auction].[ufnGetStock](@ProductID)=0) --> true
BEGIN
    SET @IND_ADD_PRODUCT = 0
    THROW 50001, 'The product is not in auction campaign discount or a product was not inserted',0
END

Error: "Msg 102, Level 15, State 1, Procedure uspAddProductToAuction, Line 14 [Batch Start Line 180] Incorrect syntax near 'THROW'."

Thank you in advance