Need Help, How To Change Datatype In Order To Sort Some Extracted Numbers From String

Hello,

I am trying to extract from some strings like the following strings the number and order them by that number:

Box 1
Box 2
Box 3
Box 20
Box 21
...(and so on)


The problem I am having is that I already extracted the number using

Substring([field],[starting position],[lenght])

but the output seems to be in a string format, so the order is not in an ascending order.

Thanks for any suggestions.