If you are on SQL 2017, you can use STRING_AGG which would work beautifully for your problem. Otherwise, use something like this:
SELECT
t1.[Order],
Product = STUFF(c.Products,1,1,'')
FROM
(SELECT DISTINCT t.[Order] FROM YourTable t) AS t1
CROSS APPLY
(
SELECT ',' + t2.Product
FROM
YourTable t2
WHERE
t1.[Order] = t2.[Order]
ORDER BY
t2.Product
FOR XML PATH('')
) c(Products)
ORDER BY
t1.[Order];