How to Get some text from the variable in ZPL Command

Question

i have created a simple zpl program. My program Using call a variable, connect with database and uploading in web, this program example:

^XA
^JMA
^PR2
^~SD20
^BY3
^LH20,10
^FO155,152^BY2^BCN,40,N,N,N^FD$USIM$^FS
^A0N,30,30^FO155,197^CI0^FH_^FDNo.SimCard:$USIM$^FS
^PQ1,0,1,Y
^XZ

And result after printing is like

*"Barcode"*
No.Simcard:123456789

My case is how to take just a few numbers in the variable at $USIM$, like a function on the LET that can take several digits from a variable, for example

LET A$="Zebra Quality Printers"

LET B$=A$(1:13)

PRINT B$

Zebra Quality

I want to be able to in my program is only take last 3 digits at $USIM$

*"BARCODE"*
No.Simcard:789

I read the Zebra documentation and it only can in ZBL command, how to convert or make it work in ZPL command ?

Please Help me,

Thank you in advance