Custom Auto increment?

Question

i searched for the solution for custom increment with prefix. im using mvc5 asp.net. my problem is to generate like this.

 

in example 1 as you can see we have 4 zero, and if we reach the example 2 we have 3 zero,

please help how to format like this. 

 

example 1: 

ORD-00001

ORD-00002

.....

example2

ORD-00010

 ....

example3

ORD-00100