You should be able address the whole string at once, though I’m rusty on my Siemens and don’t have a reference to boot up right now.
But I think its something along the lines of DB###,STRING53.30, where the numbers are your datablock number, the 53 is the address it starts and 30 is the length.
Added the manual for reference as well.
https://docs.inductiveautomation.com/display/DOC81/Siemens