order by sql query , not displaying in order

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SQL-Server

i want to display records as follow:

sr no Age Distribution
0 0 254
1 1 125
2 2 45
3 3 47
4 4 24

this is the query i am using, but it is not displaying in series, its series is 1,10,100,2,20,21,22,23

SELECT Age,COUNT(PID)AS [Age wise Distribution]
FROM [Main Data]GROUP BY Age ORDER BY Age asc