how do I get an expression to extract all numbers from an autonum.

[Z.]

I am trying to set up an expression that will extract all numbers from an
autonumbered field. The autonumbered field is formatted as 00001 so the
autonumbering will start at 00001, 00002 and so forth. I can only get my
expression to extract the 1, 2, etc. instead of the whole number 00001,
00002, etc.
Any help would be appreciated. Thanks